forked from Minki/linux
8486a7882b
Clear MNT_LOCKED in the callers of copy_tree except copy_mnt_ns, and collect_mounts. In copy_mnt_ns it is necessary to create an exact copy of a mount tree, so not clearing MNT_LOCKED is important. Similarly collect_mounts is used to take a snapshot of the mount tree for audit logging purposes and auditing using a faithful copy of the tree is important. This becomes particularly significant when we start setting MNT_LOCKED on rootfs to prevent it from being unmounted. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
3224 lines
78 KiB
C
3224 lines
78 KiB
C
/*
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* linux/fs/namespace.c
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*
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* (C) Copyright Al Viro 2000, 2001
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* Released under GPL v2.
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*
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* Based on code from fs/super.c, copyright Linus Torvalds and others.
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* Heavily rewritten.
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*/
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#include <linux/syscalls.h>
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#include <linux/export.h>
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#include <linux/capability.h>
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#include <linux/mnt_namespace.h>
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#include <linux/user_namespace.h>
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#include <linux/namei.h>
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#include <linux/security.h>
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#include <linux/idr.h>
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#include <linux/init.h> /* init_rootfs */
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#include <linux/fs_struct.h> /* get_fs_root et.al. */
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#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
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#include <linux/uaccess.h>
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#include <linux/proc_ns.h>
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#include <linux/magic.h>
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#include <linux/bootmem.h>
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#include <linux/task_work.h>
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#include "pnode.h"
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#include "internal.h"
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static unsigned int m_hash_mask __read_mostly;
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static unsigned int m_hash_shift __read_mostly;
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static unsigned int mp_hash_mask __read_mostly;
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static unsigned int mp_hash_shift __read_mostly;
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static __initdata unsigned long mhash_entries;
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static int __init set_mhash_entries(char *str)
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{
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if (!str)
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return 0;
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mhash_entries = simple_strtoul(str, &str, 0);
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return 1;
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}
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__setup("mhash_entries=", set_mhash_entries);
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static __initdata unsigned long mphash_entries;
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static int __init set_mphash_entries(char *str)
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{
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if (!str)
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return 0;
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mphash_entries = simple_strtoul(str, &str, 0);
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return 1;
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}
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__setup("mphash_entries=", set_mphash_entries);
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static u64 event;
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static DEFINE_IDA(mnt_id_ida);
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static DEFINE_IDA(mnt_group_ida);
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static DEFINE_SPINLOCK(mnt_id_lock);
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static int mnt_id_start = 0;
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static int mnt_group_start = 1;
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static struct hlist_head *mount_hashtable __read_mostly;
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static struct hlist_head *mountpoint_hashtable __read_mostly;
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static struct kmem_cache *mnt_cache __read_mostly;
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static DECLARE_RWSEM(namespace_sem);
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/* /sys/fs */
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struct kobject *fs_kobj;
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EXPORT_SYMBOL_GPL(fs_kobj);
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/*
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* vfsmount lock may be taken for read to prevent changes to the
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* vfsmount hash, ie. during mountpoint lookups or walking back
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* up the tree.
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*
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* It should be taken for write in all cases where the vfsmount
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* tree or hash is modified or when a vfsmount structure is modified.
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*/
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
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static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
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{
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unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
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tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
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tmp = tmp + (tmp >> m_hash_shift);
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return &mount_hashtable[tmp & m_hash_mask];
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}
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static inline struct hlist_head *mp_hash(struct dentry *dentry)
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{
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unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
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tmp = tmp + (tmp >> mp_hash_shift);
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return &mountpoint_hashtable[tmp & mp_hash_mask];
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}
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/*
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* allocation is serialized by namespace_sem, but we need the spinlock to
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* serialize with freeing.
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*/
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static int mnt_alloc_id(struct mount *mnt)
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{
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int res;
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retry:
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ida_pre_get(&mnt_id_ida, GFP_KERNEL);
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spin_lock(&mnt_id_lock);
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res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
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if (!res)
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mnt_id_start = mnt->mnt_id + 1;
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spin_unlock(&mnt_id_lock);
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if (res == -EAGAIN)
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goto retry;
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return res;
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}
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static void mnt_free_id(struct mount *mnt)
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{
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int id = mnt->mnt_id;
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spin_lock(&mnt_id_lock);
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ida_remove(&mnt_id_ida, id);
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if (mnt_id_start > id)
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mnt_id_start = id;
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spin_unlock(&mnt_id_lock);
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}
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/*
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* Allocate a new peer group ID
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*
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* mnt_group_ida is protected by namespace_sem
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*/
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static int mnt_alloc_group_id(struct mount *mnt)
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{
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int res;
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if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
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return -ENOMEM;
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res = ida_get_new_above(&mnt_group_ida,
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mnt_group_start,
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&mnt->mnt_group_id);
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if (!res)
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mnt_group_start = mnt->mnt_group_id + 1;
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return res;
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}
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/*
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* Release a peer group ID
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*/
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void mnt_release_group_id(struct mount *mnt)
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{
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int id = mnt->mnt_group_id;
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ida_remove(&mnt_group_ida, id);
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if (mnt_group_start > id)
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mnt_group_start = id;
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mnt->mnt_group_id = 0;
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}
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/*
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* vfsmount lock must be held for read
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*/
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static inline void mnt_add_count(struct mount *mnt, int n)
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{
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#ifdef CONFIG_SMP
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this_cpu_add(mnt->mnt_pcp->mnt_count, n);
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#else
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preempt_disable();
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mnt->mnt_count += n;
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preempt_enable();
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#endif
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}
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/*
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* vfsmount lock must be held for write
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*/
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unsigned int mnt_get_count(struct mount *mnt)
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{
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#ifdef CONFIG_SMP
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unsigned int count = 0;
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int cpu;
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for_each_possible_cpu(cpu) {
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count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
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}
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return count;
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#else
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return mnt->mnt_count;
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#endif
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}
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static struct mount *alloc_vfsmnt(const char *name)
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{
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struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
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if (mnt) {
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int err;
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err = mnt_alloc_id(mnt);
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if (err)
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goto out_free_cache;
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if (name) {
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mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
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if (!mnt->mnt_devname)
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goto out_free_id;
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}
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#ifdef CONFIG_SMP
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mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
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if (!mnt->mnt_pcp)
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goto out_free_devname;
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this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
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#else
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mnt->mnt_count = 1;
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mnt->mnt_writers = 0;
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#endif
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INIT_HLIST_NODE(&mnt->mnt_hash);
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INIT_LIST_HEAD(&mnt->mnt_child);
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INIT_LIST_HEAD(&mnt->mnt_mounts);
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INIT_LIST_HEAD(&mnt->mnt_list);
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INIT_LIST_HEAD(&mnt->mnt_expire);
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INIT_LIST_HEAD(&mnt->mnt_share);
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INIT_LIST_HEAD(&mnt->mnt_slave_list);
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INIT_LIST_HEAD(&mnt->mnt_slave);
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INIT_HLIST_NODE(&mnt->mnt_mp_list);
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#ifdef CONFIG_FSNOTIFY
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INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
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#endif
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}
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return mnt;
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#ifdef CONFIG_SMP
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out_free_devname:
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kfree(mnt->mnt_devname);
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#endif
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out_free_id:
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mnt_free_id(mnt);
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out_free_cache:
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kmem_cache_free(mnt_cache, mnt);
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return NULL;
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}
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/*
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* Most r/o checks on a fs are for operations that take
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* discrete amounts of time, like a write() or unlink().
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* We must keep track of when those operations start
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* (for permission checks) and when they end, so that
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* we can determine when writes are able to occur to
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* a filesystem.
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*/
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/*
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* __mnt_is_readonly: check whether a mount is read-only
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* @mnt: the mount to check for its write status
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*
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* This shouldn't be used directly ouside of the VFS.
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* It does not guarantee that the filesystem will stay
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* r/w, just that it is right *now*. This can not and
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* should not be used in place of IS_RDONLY(inode).
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* mnt_want/drop_write() will _keep_ the filesystem
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* r/w.
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*/
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int __mnt_is_readonly(struct vfsmount *mnt)
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{
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if (mnt->mnt_flags & MNT_READONLY)
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return 1;
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if (mnt->mnt_sb->s_flags & MS_RDONLY)
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return 1;
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return 0;
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}
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EXPORT_SYMBOL_GPL(__mnt_is_readonly);
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static inline void mnt_inc_writers(struct mount *mnt)
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{
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#ifdef CONFIG_SMP
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this_cpu_inc(mnt->mnt_pcp->mnt_writers);
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#else
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mnt->mnt_writers++;
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#endif
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}
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static inline void mnt_dec_writers(struct mount *mnt)
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{
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#ifdef CONFIG_SMP
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this_cpu_dec(mnt->mnt_pcp->mnt_writers);
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#else
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mnt->mnt_writers--;
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#endif
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}
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static unsigned int mnt_get_writers(struct mount *mnt)
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{
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#ifdef CONFIG_SMP
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unsigned int count = 0;
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int cpu;
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for_each_possible_cpu(cpu) {
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count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
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}
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return count;
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#else
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return mnt->mnt_writers;
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#endif
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}
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static int mnt_is_readonly(struct vfsmount *mnt)
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{
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if (mnt->mnt_sb->s_readonly_remount)
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return 1;
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/* Order wrt setting s_flags/s_readonly_remount in do_remount() */
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smp_rmb();
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return __mnt_is_readonly(mnt);
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}
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/*
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* Most r/o & frozen checks on a fs are for operations that take discrete
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* amounts of time, like a write() or unlink(). We must keep track of when
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* those operations start (for permission checks) and when they end, so that we
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* can determine when writes are able to occur to a filesystem.
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*/
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/**
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* __mnt_want_write - get write access to a mount without freeze protection
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* @m: the mount on which to take a write
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*
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* This tells the low-level filesystem that a write is about to be performed to
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* it, and makes sure that writes are allowed (mnt it read-write) before
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* returning success. This operation does not protect against filesystem being
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* frozen. When the write operation is finished, __mnt_drop_write() must be
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* called. This is effectively a refcount.
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*/
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int __mnt_want_write(struct vfsmount *m)
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{
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struct mount *mnt = real_mount(m);
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int ret = 0;
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preempt_disable();
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mnt_inc_writers(mnt);
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/*
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* The store to mnt_inc_writers must be visible before we pass
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* MNT_WRITE_HOLD loop below, so that the slowpath can see our
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* incremented count after it has set MNT_WRITE_HOLD.
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*/
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smp_mb();
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while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
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cpu_relax();
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/*
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* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
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* be set to match its requirements. So we must not load that until
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* MNT_WRITE_HOLD is cleared.
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*/
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smp_rmb();
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if (mnt_is_readonly(m)) {
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mnt_dec_writers(mnt);
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ret = -EROFS;
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}
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preempt_enable();
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return ret;
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}
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/**
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* mnt_want_write - get write access to a mount
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* @m: the mount on which to take a write
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*
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* This tells the low-level filesystem that a write is about to be performed to
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* it, and makes sure that writes are allowed (mount is read-write, filesystem
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* is not frozen) before returning success. When the write operation is
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* finished, mnt_drop_write() must be called. This is effectively a refcount.
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*/
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int mnt_want_write(struct vfsmount *m)
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{
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int ret;
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sb_start_write(m->mnt_sb);
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ret = __mnt_want_write(m);
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if (ret)
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sb_end_write(m->mnt_sb);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mnt_want_write);
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/**
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* mnt_clone_write - get write access to a mount
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* @mnt: the mount on which to take a write
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*
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* This is effectively like mnt_want_write, except
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* it must only be used to take an extra write reference
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* on a mountpoint that we already know has a write reference
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* on it. This allows some optimisation.
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*
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* After finished, mnt_drop_write must be called as usual to
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* drop the reference.
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*/
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int mnt_clone_write(struct vfsmount *mnt)
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{
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/* superblock may be r/o */
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if (__mnt_is_readonly(mnt))
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return -EROFS;
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preempt_disable();
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mnt_inc_writers(real_mount(mnt));
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preempt_enable();
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return 0;
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}
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EXPORT_SYMBOL_GPL(mnt_clone_write);
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/**
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* __mnt_want_write_file - get write access to a file's mount
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* @file: the file who's mount on which to take a write
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*
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* This is like __mnt_want_write, but it takes a file and can
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* do some optimisations if the file is open for write already
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*/
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int __mnt_want_write_file(struct file *file)
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{
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if (!(file->f_mode & FMODE_WRITER))
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return __mnt_want_write(file->f_path.mnt);
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else
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return mnt_clone_write(file->f_path.mnt);
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}
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/**
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* mnt_want_write_file - get write access to a file's mount
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* @file: the file who's mount on which to take a write
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*
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* This is like mnt_want_write, but it takes a file and can
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* do some optimisations if the file is open for write already
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*/
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int mnt_want_write_file(struct file *file)
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{
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int ret;
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sb_start_write(file->f_path.mnt->mnt_sb);
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ret = __mnt_want_write_file(file);
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if (ret)
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sb_end_write(file->f_path.mnt->mnt_sb);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mnt_want_write_file);
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|
|
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/**
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* __mnt_drop_write - give up write access to a mount
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* @mnt: the mount on which to give up write access
|
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*
|
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* Tells the low-level filesystem that we are done
|
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* performing writes to it. Must be matched with
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* __mnt_want_write() call above.
|
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*/
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void __mnt_drop_write(struct vfsmount *mnt)
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{
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preempt_disable();
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mnt_dec_writers(real_mount(mnt));
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preempt_enable();
|
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}
|
|
|
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/**
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* mnt_drop_write - give up write access to a mount
|
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* @mnt: the mount on which to give up write access
|
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*
|
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* Tells the low-level filesystem that we are done performing writes to it and
|
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* also allows filesystem to be frozen again. Must be matched with
|
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* mnt_want_write() call above.
|
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*/
|
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void mnt_drop_write(struct vfsmount *mnt)
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{
|
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__mnt_drop_write(mnt);
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sb_end_write(mnt->mnt_sb);
|
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}
|
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EXPORT_SYMBOL_GPL(mnt_drop_write);
|
|
|
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void __mnt_drop_write_file(struct file *file)
|
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{
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__mnt_drop_write(file->f_path.mnt);
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}
|
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|
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void mnt_drop_write_file(struct file *file)
|
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{
|
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mnt_drop_write(file->f_path.mnt);
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}
|
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EXPORT_SYMBOL(mnt_drop_write_file);
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|
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static int mnt_make_readonly(struct mount *mnt)
|
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{
|
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int ret = 0;
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|
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lock_mount_hash();
|
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mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
|
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/*
|
|
* After storing MNT_WRITE_HOLD, we'll read the counters. This store
|
|
* should be visible before we do.
|
|
*/
|
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smp_mb();
|
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|
|
/*
|
|
* With writers on hold, if this value is zero, then there are
|
|
* definitely no active writers (although held writers may subsequently
|
|
* increment the count, they'll have to wait, and decrement it after
|
|
* seeing MNT_READONLY).
|
|
*
|
|
* It is OK to have counter incremented on one CPU and decremented on
|
|
* another: the sum will add up correctly. The danger would be when we
|
|
* sum up each counter, if we read a counter before it is incremented,
|
|
* but then read another CPU's count which it has been subsequently
|
|
* decremented from -- we would see more decrements than we should.
|
|
* MNT_WRITE_HOLD protects against this scenario, because
|
|
* mnt_want_write first increments count, then smp_mb, then spins on
|
|
* MNT_WRITE_HOLD, so it can't be decremented by another CPU while
|
|
* we're counting up here.
|
|
*/
|
|
if (mnt_get_writers(mnt) > 0)
|
|
ret = -EBUSY;
|
|
else
|
|
mnt->mnt.mnt_flags |= MNT_READONLY;
|
|
/*
|
|
* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
|
|
* that become unheld will see MNT_READONLY.
|
|
*/
|
|
smp_wmb();
|
|
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
|
|
unlock_mount_hash();
|
|
return ret;
|
|
}
|
|
|
|
static void __mnt_unmake_readonly(struct mount *mnt)
|
|
{
|
|
lock_mount_hash();
|
|
mnt->mnt.mnt_flags &= ~MNT_READONLY;
|
|
unlock_mount_hash();
|
|
}
|
|
|
|
int sb_prepare_remount_readonly(struct super_block *sb)
|
|
{
|
|
struct mount *mnt;
|
|
int err = 0;
|
|
|
|
/* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
|
|
if (atomic_long_read(&sb->s_remove_count))
|
|
return -EBUSY;
|
|
|
|
lock_mount_hash();
|
|
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
|
|
if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
|
|
mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
|
|
smp_mb();
|
|
if (mnt_get_writers(mnt) > 0) {
|
|
err = -EBUSY;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
if (!err && atomic_long_read(&sb->s_remove_count))
|
|
err = -EBUSY;
|
|
|
|
if (!err) {
|
|
sb->s_readonly_remount = 1;
|
|
smp_wmb();
|
|
}
|
|
list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
|
|
if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
|
|
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
|
|
}
|
|
unlock_mount_hash();
|
|
|
|
return err;
|
|
}
|
|
|
|
static void free_vfsmnt(struct mount *mnt)
|
|
{
|
|
kfree(mnt->mnt_devname);
|
|
#ifdef CONFIG_SMP
|
|
free_percpu(mnt->mnt_pcp);
|
|
#endif
|
|
kmem_cache_free(mnt_cache, mnt);
|
|
}
|
|
|
|
static void delayed_free_vfsmnt(struct rcu_head *head)
|
|
{
|
|
free_vfsmnt(container_of(head, struct mount, mnt_rcu));
|
|
}
|
|
|
|
/* call under rcu_read_lock */
|
|
bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
|
|
{
|
|
struct mount *mnt;
|
|
if (read_seqretry(&mount_lock, seq))
|
|
return false;
|
|
if (bastard == NULL)
|
|
return true;
|
|
mnt = real_mount(bastard);
|
|
mnt_add_count(mnt, 1);
|
|
if (likely(!read_seqretry(&mount_lock, seq)))
|
|
return true;
|
|
if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
|
|
mnt_add_count(mnt, -1);
|
|
return false;
|
|
}
|
|
rcu_read_unlock();
|
|
mntput(bastard);
|
|
rcu_read_lock();
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* find the first mount at @dentry on vfsmount @mnt.
|
|
* call under rcu_read_lock()
|
|
*/
|
|
struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
|
|
{
|
|
struct hlist_head *head = m_hash(mnt, dentry);
|
|
struct mount *p;
|
|
|
|
hlist_for_each_entry_rcu(p, head, mnt_hash)
|
|
if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
|
|
return p;
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* find the last mount at @dentry on vfsmount @mnt.
|
|
* mount_lock must be held.
|
|
*/
|
|
struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
|
|
{
|
|
struct mount *p, *res;
|
|
res = p = __lookup_mnt(mnt, dentry);
|
|
if (!p)
|
|
goto out;
|
|
hlist_for_each_entry_continue(p, mnt_hash) {
|
|
if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
|
|
break;
|
|
res = p;
|
|
}
|
|
out:
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* lookup_mnt - Return the first child mount mounted at path
|
|
*
|
|
* "First" means first mounted chronologically. If you create the
|
|
* following mounts:
|
|
*
|
|
* mount /dev/sda1 /mnt
|
|
* mount /dev/sda2 /mnt
|
|
* mount /dev/sda3 /mnt
|
|
*
|
|
* Then lookup_mnt() on the base /mnt dentry in the root mount will
|
|
* return successively the root dentry and vfsmount of /dev/sda1, then
|
|
* /dev/sda2, then /dev/sda3, then NULL.
|
|
*
|
|
* lookup_mnt takes a reference to the found vfsmount.
|
|
*/
|
|
struct vfsmount *lookup_mnt(struct path *path)
|
|
{
|
|
struct mount *child_mnt;
|
|
struct vfsmount *m;
|
|
unsigned seq;
|
|
|
|
rcu_read_lock();
|
|
do {
|
|
seq = read_seqbegin(&mount_lock);
|
|
child_mnt = __lookup_mnt(path->mnt, path->dentry);
|
|
m = child_mnt ? &child_mnt->mnt : NULL;
|
|
} while (!legitimize_mnt(m, seq));
|
|
rcu_read_unlock();
|
|
return m;
|
|
}
|
|
|
|
/*
|
|
* __is_local_mountpoint - Test to see if dentry is a mountpoint in the
|
|
* current mount namespace.
|
|
*
|
|
* The common case is dentries are not mountpoints at all and that
|
|
* test is handled inline. For the slow case when we are actually
|
|
* dealing with a mountpoint of some kind, walk through all of the
|
|
* mounts in the current mount namespace and test to see if the dentry
|
|
* is a mountpoint.
|
|
*
|
|
* The mount_hashtable is not usable in the context because we
|
|
* need to identify all mounts that may be in the current mount
|
|
* namespace not just a mount that happens to have some specified
|
|
* parent mount.
|
|
*/
|
|
bool __is_local_mountpoint(struct dentry *dentry)
|
|
{
|
|
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
|
|
struct mount *mnt;
|
|
bool is_covered = false;
|
|
|
|
if (!d_mountpoint(dentry))
|
|
goto out;
|
|
|
|
down_read(&namespace_sem);
|
|
list_for_each_entry(mnt, &ns->list, mnt_list) {
|
|
is_covered = (mnt->mnt_mountpoint == dentry);
|
|
if (is_covered)
|
|
break;
|
|
}
|
|
up_read(&namespace_sem);
|
|
out:
|
|
return is_covered;
|
|
}
|
|
|
|
static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
|
|
{
|
|
struct hlist_head *chain = mp_hash(dentry);
|
|
struct mountpoint *mp;
|
|
|
|
hlist_for_each_entry(mp, chain, m_hash) {
|
|
if (mp->m_dentry == dentry) {
|
|
/* might be worth a WARN_ON() */
|
|
if (d_unlinked(dentry))
|
|
return ERR_PTR(-ENOENT);
|
|
mp->m_count++;
|
|
return mp;
|
|
}
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static struct mountpoint *new_mountpoint(struct dentry *dentry)
|
|
{
|
|
struct hlist_head *chain = mp_hash(dentry);
|
|
struct mountpoint *mp;
|
|
int ret;
|
|
|
|
mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
|
|
if (!mp)
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
ret = d_set_mounted(dentry);
|
|
if (ret) {
|
|
kfree(mp);
|
|
return ERR_PTR(ret);
|
|
}
|
|
|
|
mp->m_dentry = dentry;
|
|
mp->m_count = 1;
|
|
hlist_add_head(&mp->m_hash, chain);
|
|
INIT_HLIST_HEAD(&mp->m_list);
|
|
return mp;
|
|
}
|
|
|
|
static void put_mountpoint(struct mountpoint *mp)
|
|
{
|
|
if (!--mp->m_count) {
|
|
struct dentry *dentry = mp->m_dentry;
|
|
BUG_ON(!hlist_empty(&mp->m_list));
|
|
spin_lock(&dentry->d_lock);
|
|
dentry->d_flags &= ~DCACHE_MOUNTED;
|
|
spin_unlock(&dentry->d_lock);
|
|
hlist_del(&mp->m_hash);
|
|
kfree(mp);
|
|
}
|
|
}
|
|
|
|
static inline int check_mnt(struct mount *mnt)
|
|
{
|
|
return mnt->mnt_ns == current->nsproxy->mnt_ns;
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
static void touch_mnt_namespace(struct mnt_namespace *ns)
|
|
{
|
|
if (ns) {
|
|
ns->event = ++event;
|
|
wake_up_interruptible(&ns->poll);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
static void __touch_mnt_namespace(struct mnt_namespace *ns)
|
|
{
|
|
if (ns && ns->event != event) {
|
|
ns->event = event;
|
|
wake_up_interruptible(&ns->poll);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
static void detach_mnt(struct mount *mnt, struct path *old_path)
|
|
{
|
|
old_path->dentry = mnt->mnt_mountpoint;
|
|
old_path->mnt = &mnt->mnt_parent->mnt;
|
|
mnt->mnt_parent = mnt;
|
|
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
|
|
list_del_init(&mnt->mnt_child);
|
|
hlist_del_init_rcu(&mnt->mnt_hash);
|
|
hlist_del_init(&mnt->mnt_mp_list);
|
|
put_mountpoint(mnt->mnt_mp);
|
|
mnt->mnt_mp = NULL;
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
void mnt_set_mountpoint(struct mount *mnt,
|
|
struct mountpoint *mp,
|
|
struct mount *child_mnt)
|
|
{
|
|
mp->m_count++;
|
|
mnt_add_count(mnt, 1); /* essentially, that's mntget */
|
|
child_mnt->mnt_mountpoint = dget(mp->m_dentry);
|
|
child_mnt->mnt_parent = mnt;
|
|
child_mnt->mnt_mp = mp;
|
|
hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
static void attach_mnt(struct mount *mnt,
|
|
struct mount *parent,
|
|
struct mountpoint *mp)
|
|
{
|
|
mnt_set_mountpoint(parent, mp, mnt);
|
|
hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
|
|
list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
|
|
}
|
|
|
|
static void attach_shadowed(struct mount *mnt,
|
|
struct mount *parent,
|
|
struct mount *shadows)
|
|
{
|
|
if (shadows) {
|
|
hlist_add_behind_rcu(&mnt->mnt_hash, &shadows->mnt_hash);
|
|
list_add(&mnt->mnt_child, &shadows->mnt_child);
|
|
} else {
|
|
hlist_add_head_rcu(&mnt->mnt_hash,
|
|
m_hash(&parent->mnt, mnt->mnt_mountpoint));
|
|
list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
static void commit_tree(struct mount *mnt, struct mount *shadows)
|
|
{
|
|
struct mount *parent = mnt->mnt_parent;
|
|
struct mount *m;
|
|
LIST_HEAD(head);
|
|
struct mnt_namespace *n = parent->mnt_ns;
|
|
|
|
BUG_ON(parent == mnt);
|
|
|
|
list_add_tail(&head, &mnt->mnt_list);
|
|
list_for_each_entry(m, &head, mnt_list)
|
|
m->mnt_ns = n;
|
|
|
|
list_splice(&head, n->list.prev);
|
|
|
|
attach_shadowed(mnt, parent, shadows);
|
|
touch_mnt_namespace(n);
|
|
}
|
|
|
|
static struct mount *next_mnt(struct mount *p, struct mount *root)
|
|
{
|
|
struct list_head *next = p->mnt_mounts.next;
|
|
if (next == &p->mnt_mounts) {
|
|
while (1) {
|
|
if (p == root)
|
|
return NULL;
|
|
next = p->mnt_child.next;
|
|
if (next != &p->mnt_parent->mnt_mounts)
|
|
break;
|
|
p = p->mnt_parent;
|
|
}
|
|
}
|
|
return list_entry(next, struct mount, mnt_child);
|
|
}
|
|
|
|
static struct mount *skip_mnt_tree(struct mount *p)
|
|
{
|
|
struct list_head *prev = p->mnt_mounts.prev;
|
|
while (prev != &p->mnt_mounts) {
|
|
p = list_entry(prev, struct mount, mnt_child);
|
|
prev = p->mnt_mounts.prev;
|
|
}
|
|
return p;
|
|
}
|
|
|
|
struct vfsmount *
|
|
vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
|
|
{
|
|
struct mount *mnt;
|
|
struct dentry *root;
|
|
|
|
if (!type)
|
|
return ERR_PTR(-ENODEV);
|
|
|
|
mnt = alloc_vfsmnt(name);
|
|
if (!mnt)
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
if (flags & MS_KERNMOUNT)
|
|
mnt->mnt.mnt_flags = MNT_INTERNAL;
|
|
|
|
root = mount_fs(type, flags, name, data);
|
|
if (IS_ERR(root)) {
|
|
mnt_free_id(mnt);
|
|
free_vfsmnt(mnt);
|
|
return ERR_CAST(root);
|
|
}
|
|
|
|
mnt->mnt.mnt_root = root;
|
|
mnt->mnt.mnt_sb = root->d_sb;
|
|
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
|
|
mnt->mnt_parent = mnt;
|
|
lock_mount_hash();
|
|
list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
|
|
unlock_mount_hash();
|
|
return &mnt->mnt;
|
|
}
|
|
EXPORT_SYMBOL_GPL(vfs_kern_mount);
|
|
|
|
static struct mount *clone_mnt(struct mount *old, struct dentry *root,
|
|
int flag)
|
|
{
|
|
struct super_block *sb = old->mnt.mnt_sb;
|
|
struct mount *mnt;
|
|
int err;
|
|
|
|
mnt = alloc_vfsmnt(old->mnt_devname);
|
|
if (!mnt)
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
|
|
mnt->mnt_group_id = 0; /* not a peer of original */
|
|
else
|
|
mnt->mnt_group_id = old->mnt_group_id;
|
|
|
|
if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
|
|
err = mnt_alloc_group_id(mnt);
|
|
if (err)
|
|
goto out_free;
|
|
}
|
|
|
|
mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~(MNT_WRITE_HOLD|MNT_MARKED);
|
|
/* Don't allow unprivileged users to change mount flags */
|
|
if (flag & CL_UNPRIVILEGED) {
|
|
mnt->mnt.mnt_flags |= MNT_LOCK_ATIME;
|
|
|
|
if (mnt->mnt.mnt_flags & MNT_READONLY)
|
|
mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
|
|
|
|
if (mnt->mnt.mnt_flags & MNT_NODEV)
|
|
mnt->mnt.mnt_flags |= MNT_LOCK_NODEV;
|
|
|
|
if (mnt->mnt.mnt_flags & MNT_NOSUID)
|
|
mnt->mnt.mnt_flags |= MNT_LOCK_NOSUID;
|
|
|
|
if (mnt->mnt.mnt_flags & MNT_NOEXEC)
|
|
mnt->mnt.mnt_flags |= MNT_LOCK_NOEXEC;
|
|
}
|
|
|
|
/* Don't allow unprivileged users to reveal what is under a mount */
|
|
if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
|
|
mnt->mnt.mnt_flags |= MNT_LOCKED;
|
|
|
|
atomic_inc(&sb->s_active);
|
|
mnt->mnt.mnt_sb = sb;
|
|
mnt->mnt.mnt_root = dget(root);
|
|
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
|
|
mnt->mnt_parent = mnt;
|
|
lock_mount_hash();
|
|
list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
|
|
unlock_mount_hash();
|
|
|
|
if ((flag & CL_SLAVE) ||
|
|
((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
|
|
list_add(&mnt->mnt_slave, &old->mnt_slave_list);
|
|
mnt->mnt_master = old;
|
|
CLEAR_MNT_SHARED(mnt);
|
|
} else if (!(flag & CL_PRIVATE)) {
|
|
if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
|
|
list_add(&mnt->mnt_share, &old->mnt_share);
|
|
if (IS_MNT_SLAVE(old))
|
|
list_add(&mnt->mnt_slave, &old->mnt_slave);
|
|
mnt->mnt_master = old->mnt_master;
|
|
}
|
|
if (flag & CL_MAKE_SHARED)
|
|
set_mnt_shared(mnt);
|
|
|
|
/* stick the duplicate mount on the same expiry list
|
|
* as the original if that was on one */
|
|
if (flag & CL_EXPIRE) {
|
|
if (!list_empty(&old->mnt_expire))
|
|
list_add(&mnt->mnt_expire, &old->mnt_expire);
|
|
}
|
|
|
|
return mnt;
|
|
|
|
out_free:
|
|
mnt_free_id(mnt);
|
|
free_vfsmnt(mnt);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
static void cleanup_mnt(struct mount *mnt)
|
|
{
|
|
/*
|
|
* This probably indicates that somebody messed
|
|
* up a mnt_want/drop_write() pair. If this
|
|
* happens, the filesystem was probably unable
|
|
* to make r/w->r/o transitions.
|
|
*/
|
|
/*
|
|
* The locking used to deal with mnt_count decrement provides barriers,
|
|
* so mnt_get_writers() below is safe.
|
|
*/
|
|
WARN_ON(mnt_get_writers(mnt));
|
|
if (unlikely(mnt->mnt_pins.first))
|
|
mnt_pin_kill(mnt);
|
|
fsnotify_vfsmount_delete(&mnt->mnt);
|
|
dput(mnt->mnt.mnt_root);
|
|
deactivate_super(mnt->mnt.mnt_sb);
|
|
mnt_free_id(mnt);
|
|
call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
|
|
}
|
|
|
|
static void __cleanup_mnt(struct rcu_head *head)
|
|
{
|
|
cleanup_mnt(container_of(head, struct mount, mnt_rcu));
|
|
}
|
|
|
|
static LLIST_HEAD(delayed_mntput_list);
|
|
static void delayed_mntput(struct work_struct *unused)
|
|
{
|
|
struct llist_node *node = llist_del_all(&delayed_mntput_list);
|
|
struct llist_node *next;
|
|
|
|
for (; node; node = next) {
|
|
next = llist_next(node);
|
|
cleanup_mnt(llist_entry(node, struct mount, mnt_llist));
|
|
}
|
|
}
|
|
static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
|
|
|
|
static void mntput_no_expire(struct mount *mnt)
|
|
{
|
|
rcu_read_lock();
|
|
mnt_add_count(mnt, -1);
|
|
if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
|
|
rcu_read_unlock();
|
|
return;
|
|
}
|
|
lock_mount_hash();
|
|
if (mnt_get_count(mnt)) {
|
|
rcu_read_unlock();
|
|
unlock_mount_hash();
|
|
return;
|
|
}
|
|
if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
|
|
rcu_read_unlock();
|
|
unlock_mount_hash();
|
|
return;
|
|
}
|
|
mnt->mnt.mnt_flags |= MNT_DOOMED;
|
|
rcu_read_unlock();
|
|
|
|
list_del(&mnt->mnt_instance);
|
|
unlock_mount_hash();
|
|
|
|
if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
|
|
struct task_struct *task = current;
|
|
if (likely(!(task->flags & PF_KTHREAD))) {
|
|
init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
|
|
if (!task_work_add(task, &mnt->mnt_rcu, true))
|
|
return;
|
|
}
|
|
if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
|
|
schedule_delayed_work(&delayed_mntput_work, 1);
|
|
return;
|
|
}
|
|
cleanup_mnt(mnt);
|
|
}
|
|
|
|
void mntput(struct vfsmount *mnt)
|
|
{
|
|
if (mnt) {
|
|
struct mount *m = real_mount(mnt);
|
|
/* avoid cacheline pingpong, hope gcc doesn't get "smart" */
|
|
if (unlikely(m->mnt_expiry_mark))
|
|
m->mnt_expiry_mark = 0;
|
|
mntput_no_expire(m);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(mntput);
|
|
|
|
struct vfsmount *mntget(struct vfsmount *mnt)
|
|
{
|
|
if (mnt)
|
|
mnt_add_count(real_mount(mnt), 1);
|
|
return mnt;
|
|
}
|
|
EXPORT_SYMBOL(mntget);
|
|
|
|
struct vfsmount *mnt_clone_internal(struct path *path)
|
|
{
|
|
struct mount *p;
|
|
p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
|
|
if (IS_ERR(p))
|
|
return ERR_CAST(p);
|
|
p->mnt.mnt_flags |= MNT_INTERNAL;
|
|
return &p->mnt;
|
|
}
|
|
|
|
static inline void mangle(struct seq_file *m, const char *s)
|
|
{
|
|
seq_escape(m, s, " \t\n\\");
|
|
}
|
|
|
|
/*
|
|
* Simple .show_options callback for filesystems which don't want to
|
|
* implement more complex mount option showing.
|
|
*
|
|
* See also save_mount_options().
|
|
*/
|
|
int generic_show_options(struct seq_file *m, struct dentry *root)
|
|
{
|
|
const char *options;
|
|
|
|
rcu_read_lock();
|
|
options = rcu_dereference(root->d_sb->s_options);
|
|
|
|
if (options != NULL && options[0]) {
|
|
seq_putc(m, ',');
|
|
mangle(m, options);
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(generic_show_options);
|
|
|
|
/*
|
|
* If filesystem uses generic_show_options(), this function should be
|
|
* called from the fill_super() callback.
|
|
*
|
|
* The .remount_fs callback usually needs to be handled in a special
|
|
* way, to make sure, that previous options are not overwritten if the
|
|
* remount fails.
|
|
*
|
|
* Also note, that if the filesystem's .remount_fs function doesn't
|
|
* reset all options to their default value, but changes only newly
|
|
* given options, then the displayed options will not reflect reality
|
|
* any more.
|
|
*/
|
|
void save_mount_options(struct super_block *sb, char *options)
|
|
{
|
|
BUG_ON(sb->s_options);
|
|
rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
|
|
}
|
|
EXPORT_SYMBOL(save_mount_options);
|
|
|
|
void replace_mount_options(struct super_block *sb, char *options)
|
|
{
|
|
char *old = sb->s_options;
|
|
rcu_assign_pointer(sb->s_options, options);
|
|
if (old) {
|
|
synchronize_rcu();
|
|
kfree(old);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(replace_mount_options);
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
/* iterator; we want it to have access to namespace_sem, thus here... */
|
|
static void *m_start(struct seq_file *m, loff_t *pos)
|
|
{
|
|
struct proc_mounts *p = proc_mounts(m);
|
|
|
|
down_read(&namespace_sem);
|
|
if (p->cached_event == p->ns->event) {
|
|
void *v = p->cached_mount;
|
|
if (*pos == p->cached_index)
|
|
return v;
|
|
if (*pos == p->cached_index + 1) {
|
|
v = seq_list_next(v, &p->ns->list, &p->cached_index);
|
|
return p->cached_mount = v;
|
|
}
|
|
}
|
|
|
|
p->cached_event = p->ns->event;
|
|
p->cached_mount = seq_list_start(&p->ns->list, *pos);
|
|
p->cached_index = *pos;
|
|
return p->cached_mount;
|
|
}
|
|
|
|
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
|
|
{
|
|
struct proc_mounts *p = proc_mounts(m);
|
|
|
|
p->cached_mount = seq_list_next(v, &p->ns->list, pos);
|
|
p->cached_index = *pos;
|
|
return p->cached_mount;
|
|
}
|
|
|
|
static void m_stop(struct seq_file *m, void *v)
|
|
{
|
|
up_read(&namespace_sem);
|
|
}
|
|
|
|
static int m_show(struct seq_file *m, void *v)
|
|
{
|
|
struct proc_mounts *p = proc_mounts(m);
|
|
struct mount *r = list_entry(v, struct mount, mnt_list);
|
|
return p->show(m, &r->mnt);
|
|
}
|
|
|
|
const struct seq_operations mounts_op = {
|
|
.start = m_start,
|
|
.next = m_next,
|
|
.stop = m_stop,
|
|
.show = m_show,
|
|
};
|
|
#endif /* CONFIG_PROC_FS */
|
|
|
|
/**
|
|
* may_umount_tree - check if a mount tree is busy
|
|
* @mnt: root of mount tree
|
|
*
|
|
* This is called to check if a tree of mounts has any
|
|
* open files, pwds, chroots or sub mounts that are
|
|
* busy.
|
|
*/
|
|
int may_umount_tree(struct vfsmount *m)
|
|
{
|
|
struct mount *mnt = real_mount(m);
|
|
int actual_refs = 0;
|
|
int minimum_refs = 0;
|
|
struct mount *p;
|
|
BUG_ON(!m);
|
|
|
|
/* write lock needed for mnt_get_count */
|
|
lock_mount_hash();
|
|
for (p = mnt; p; p = next_mnt(p, mnt)) {
|
|
actual_refs += mnt_get_count(p);
|
|
minimum_refs += 2;
|
|
}
|
|
unlock_mount_hash();
|
|
|
|
if (actual_refs > minimum_refs)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
EXPORT_SYMBOL(may_umount_tree);
|
|
|
|
/**
|
|
* may_umount - check if a mount point is busy
|
|
* @mnt: root of mount
|
|
*
|
|
* This is called to check if a mount point has any
|
|
* open files, pwds, chroots or sub mounts. If the
|
|
* mount has sub mounts this will return busy
|
|
* regardless of whether the sub mounts are busy.
|
|
*
|
|
* Doesn't take quota and stuff into account. IOW, in some cases it will
|
|
* give false negatives. The main reason why it's here is that we need
|
|
* a non-destructive way to look for easily umountable filesystems.
|
|
*/
|
|
int may_umount(struct vfsmount *mnt)
|
|
{
|
|
int ret = 1;
|
|
down_read(&namespace_sem);
|
|
lock_mount_hash();
|
|
if (propagate_mount_busy(real_mount(mnt), 2))
|
|
ret = 0;
|
|
unlock_mount_hash();
|
|
up_read(&namespace_sem);
|
|
return ret;
|
|
}
|
|
|
|
EXPORT_SYMBOL(may_umount);
|
|
|
|
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
|
|
|
|
static void namespace_unlock(void)
|
|
{
|
|
struct mount *mnt;
|
|
struct hlist_head head = unmounted;
|
|
|
|
if (likely(hlist_empty(&head))) {
|
|
up_write(&namespace_sem);
|
|
return;
|
|
}
|
|
|
|
head.first->pprev = &head.first;
|
|
INIT_HLIST_HEAD(&unmounted);
|
|
|
|
/* undo decrements we'd done in umount_tree() */
|
|
hlist_for_each_entry(mnt, &head, mnt_hash)
|
|
if (mnt->mnt_ex_mountpoint.mnt)
|
|
mntget(mnt->mnt_ex_mountpoint.mnt);
|
|
|
|
up_write(&namespace_sem);
|
|
|
|
synchronize_rcu();
|
|
|
|
while (!hlist_empty(&head)) {
|
|
mnt = hlist_entry(head.first, struct mount, mnt_hash);
|
|
hlist_del_init(&mnt->mnt_hash);
|
|
if (mnt->mnt_ex_mountpoint.mnt)
|
|
path_put(&mnt->mnt_ex_mountpoint);
|
|
mntput(&mnt->mnt);
|
|
}
|
|
}
|
|
|
|
static inline void namespace_lock(void)
|
|
{
|
|
down_write(&namespace_sem);
|
|
}
|
|
|
|
/*
|
|
* mount_lock must be held
|
|
* namespace_sem must be held for write
|
|
* how = 0 => just this tree, don't propagate
|
|
* how = 1 => propagate; we know that nobody else has reference to any victims
|
|
* how = 2 => lazy umount
|
|
*/
|
|
void umount_tree(struct mount *mnt, int how)
|
|
{
|
|
HLIST_HEAD(tmp_list);
|
|
struct mount *p;
|
|
struct mount *last = NULL;
|
|
|
|
for (p = mnt; p; p = next_mnt(p, mnt)) {
|
|
hlist_del_init_rcu(&p->mnt_hash);
|
|
hlist_add_head(&p->mnt_hash, &tmp_list);
|
|
}
|
|
|
|
hlist_for_each_entry(p, &tmp_list, mnt_hash)
|
|
list_del_init(&p->mnt_child);
|
|
|
|
if (how)
|
|
propagate_umount(&tmp_list);
|
|
|
|
hlist_for_each_entry(p, &tmp_list, mnt_hash) {
|
|
list_del_init(&p->mnt_expire);
|
|
list_del_init(&p->mnt_list);
|
|
__touch_mnt_namespace(p->mnt_ns);
|
|
p->mnt_ns = NULL;
|
|
if (how < 2)
|
|
p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
|
|
if (mnt_has_parent(p)) {
|
|
hlist_del_init(&p->mnt_mp_list);
|
|
put_mountpoint(p->mnt_mp);
|
|
mnt_add_count(p->mnt_parent, -1);
|
|
/* move the reference to mountpoint into ->mnt_ex_mountpoint */
|
|
p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint;
|
|
p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt;
|
|
p->mnt_mountpoint = p->mnt.mnt_root;
|
|
p->mnt_parent = p;
|
|
p->mnt_mp = NULL;
|
|
}
|
|
change_mnt_propagation(p, MS_PRIVATE);
|
|
last = p;
|
|
}
|
|
if (last) {
|
|
last->mnt_hash.next = unmounted.first;
|
|
unmounted.first = tmp_list.first;
|
|
unmounted.first->pprev = &unmounted.first;
|
|
}
|
|
}
|
|
|
|
static void shrink_submounts(struct mount *mnt);
|
|
|
|
static int do_umount(struct mount *mnt, int flags)
|
|
{
|
|
struct super_block *sb = mnt->mnt.mnt_sb;
|
|
int retval;
|
|
|
|
retval = security_sb_umount(&mnt->mnt, flags);
|
|
if (retval)
|
|
return retval;
|
|
|
|
/*
|
|
* Allow userspace to request a mountpoint be expired rather than
|
|
* unmounting unconditionally. Unmount only happens if:
|
|
* (1) the mark is already set (the mark is cleared by mntput())
|
|
* (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
|
|
*/
|
|
if (flags & MNT_EXPIRE) {
|
|
if (&mnt->mnt == current->fs->root.mnt ||
|
|
flags & (MNT_FORCE | MNT_DETACH))
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* probably don't strictly need the lock here if we examined
|
|
* all race cases, but it's a slowpath.
|
|
*/
|
|
lock_mount_hash();
|
|
if (mnt_get_count(mnt) != 2) {
|
|
unlock_mount_hash();
|
|
return -EBUSY;
|
|
}
|
|
unlock_mount_hash();
|
|
|
|
if (!xchg(&mnt->mnt_expiry_mark, 1))
|
|
return -EAGAIN;
|
|
}
|
|
|
|
/*
|
|
* If we may have to abort operations to get out of this
|
|
* mount, and they will themselves hold resources we must
|
|
* allow the fs to do things. In the Unix tradition of
|
|
* 'Gee thats tricky lets do it in userspace' the umount_begin
|
|
* might fail to complete on the first run through as other tasks
|
|
* must return, and the like. Thats for the mount program to worry
|
|
* about for the moment.
|
|
*/
|
|
|
|
if (flags & MNT_FORCE && sb->s_op->umount_begin) {
|
|
sb->s_op->umount_begin(sb);
|
|
}
|
|
|
|
/*
|
|
* No sense to grab the lock for this test, but test itself looks
|
|
* somewhat bogus. Suggestions for better replacement?
|
|
* Ho-hum... In principle, we might treat that as umount + switch
|
|
* to rootfs. GC would eventually take care of the old vfsmount.
|
|
* Actually it makes sense, especially if rootfs would contain a
|
|
* /reboot - static binary that would close all descriptors and
|
|
* call reboot(9). Then init(8) could umount root and exec /reboot.
|
|
*/
|
|
if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
|
|
/*
|
|
* Special case for "unmounting" root ...
|
|
* we just try to remount it readonly.
|
|
*/
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
down_write(&sb->s_umount);
|
|
if (!(sb->s_flags & MS_RDONLY))
|
|
retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
|
|
up_write(&sb->s_umount);
|
|
return retval;
|
|
}
|
|
|
|
namespace_lock();
|
|
lock_mount_hash();
|
|
event++;
|
|
|
|
if (flags & MNT_DETACH) {
|
|
if (!list_empty(&mnt->mnt_list))
|
|
umount_tree(mnt, 2);
|
|
retval = 0;
|
|
} else {
|
|
shrink_submounts(mnt);
|
|
retval = -EBUSY;
|
|
if (!propagate_mount_busy(mnt, 2)) {
|
|
if (!list_empty(&mnt->mnt_list))
|
|
umount_tree(mnt, 1);
|
|
retval = 0;
|
|
}
|
|
}
|
|
unlock_mount_hash();
|
|
namespace_unlock();
|
|
return retval;
|
|
}
|
|
|
|
/*
|
|
* __detach_mounts - lazily unmount all mounts on the specified dentry
|
|
*
|
|
* During unlink, rmdir, and d_drop it is possible to loose the path
|
|
* to an existing mountpoint, and wind up leaking the mount.
|
|
* detach_mounts allows lazily unmounting those mounts instead of
|
|
* leaking them.
|
|
*
|
|
* The caller may hold dentry->d_inode->i_mutex.
|
|
*/
|
|
void __detach_mounts(struct dentry *dentry)
|
|
{
|
|
struct mountpoint *mp;
|
|
struct mount *mnt;
|
|
|
|
namespace_lock();
|
|
mp = lookup_mountpoint(dentry);
|
|
if (!mp)
|
|
goto out_unlock;
|
|
|
|
lock_mount_hash();
|
|
while (!hlist_empty(&mp->m_list)) {
|
|
mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
|
|
umount_tree(mnt, 2);
|
|
}
|
|
unlock_mount_hash();
|
|
put_mountpoint(mp);
|
|
out_unlock:
|
|
namespace_unlock();
|
|
}
|
|
|
|
/*
|
|
* Is the caller allowed to modify his namespace?
|
|
*/
|
|
static inline bool may_mount(void)
|
|
{
|
|
return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
|
|
}
|
|
|
|
/*
|
|
* Now umount can handle mount points as well as block devices.
|
|
* This is important for filesystems which use unnamed block devices.
|
|
*
|
|
* We now support a flag for forced unmount like the other 'big iron'
|
|
* unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
|
|
*/
|
|
|
|
SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
|
|
{
|
|
struct path path;
|
|
struct mount *mnt;
|
|
int retval;
|
|
int lookup_flags = 0;
|
|
|
|
if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
|
|
return -EINVAL;
|
|
|
|
if (!may_mount())
|
|
return -EPERM;
|
|
|
|
if (!(flags & UMOUNT_NOFOLLOW))
|
|
lookup_flags |= LOOKUP_FOLLOW;
|
|
|
|
retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
|
|
if (retval)
|
|
goto out;
|
|
mnt = real_mount(path.mnt);
|
|
retval = -EINVAL;
|
|
if (path.dentry != path.mnt->mnt_root)
|
|
goto dput_and_out;
|
|
if (!check_mnt(mnt))
|
|
goto dput_and_out;
|
|
if (mnt->mnt.mnt_flags & MNT_LOCKED)
|
|
goto dput_and_out;
|
|
retval = -EPERM;
|
|
if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
|
|
goto dput_and_out;
|
|
|
|
retval = do_umount(mnt, flags);
|
|
dput_and_out:
|
|
/* we mustn't call path_put() as that would clear mnt_expiry_mark */
|
|
dput(path.dentry);
|
|
mntput_no_expire(mnt);
|
|
out:
|
|
return retval;
|
|
}
|
|
|
|
#ifdef __ARCH_WANT_SYS_OLDUMOUNT
|
|
|
|
/*
|
|
* The 2.0 compatible umount. No flags.
|
|
*/
|
|
SYSCALL_DEFINE1(oldumount, char __user *, name)
|
|
{
|
|
return sys_umount(name, 0);
|
|
}
|
|
|
|
#endif
|
|
|
|
static bool is_mnt_ns_file(struct dentry *dentry)
|
|
{
|
|
/* Is this a proxy for a mount namespace? */
|
|
struct inode *inode = dentry->d_inode;
|
|
struct proc_ns *ei;
|
|
|
|
if (!proc_ns_inode(inode))
|
|
return false;
|
|
|
|
ei = get_proc_ns(inode);
|
|
if (ei->ns_ops != &mntns_operations)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool mnt_ns_loop(struct dentry *dentry)
|
|
{
|
|
/* Could bind mounting the mount namespace inode cause a
|
|
* mount namespace loop?
|
|
*/
|
|
struct mnt_namespace *mnt_ns;
|
|
if (!is_mnt_ns_file(dentry))
|
|
return false;
|
|
|
|
mnt_ns = get_proc_ns(dentry->d_inode)->ns;
|
|
return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
|
|
}
|
|
|
|
struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
|
|
int flag)
|
|
{
|
|
struct mount *res, *p, *q, *r, *parent;
|
|
|
|
if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
res = q = clone_mnt(mnt, dentry, flag);
|
|
if (IS_ERR(q))
|
|
return q;
|
|
|
|
q->mnt_mountpoint = mnt->mnt_mountpoint;
|
|
|
|
p = mnt;
|
|
list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
|
|
struct mount *s;
|
|
if (!is_subdir(r->mnt_mountpoint, dentry))
|
|
continue;
|
|
|
|
for (s = r; s; s = next_mnt(s, r)) {
|
|
struct mount *t = NULL;
|
|
if (!(flag & CL_COPY_UNBINDABLE) &&
|
|
IS_MNT_UNBINDABLE(s)) {
|
|
s = skip_mnt_tree(s);
|
|
continue;
|
|
}
|
|
if (!(flag & CL_COPY_MNT_NS_FILE) &&
|
|
is_mnt_ns_file(s->mnt.mnt_root)) {
|
|
s = skip_mnt_tree(s);
|
|
continue;
|
|
}
|
|
while (p != s->mnt_parent) {
|
|
p = p->mnt_parent;
|
|
q = q->mnt_parent;
|
|
}
|
|
p = s;
|
|
parent = q;
|
|
q = clone_mnt(p, p->mnt.mnt_root, flag);
|
|
if (IS_ERR(q))
|
|
goto out;
|
|
lock_mount_hash();
|
|
list_add_tail(&q->mnt_list, &res->mnt_list);
|
|
mnt_set_mountpoint(parent, p->mnt_mp, q);
|
|
if (!list_empty(&parent->mnt_mounts)) {
|
|
t = list_last_entry(&parent->mnt_mounts,
|
|
struct mount, mnt_child);
|
|
if (t->mnt_mp != p->mnt_mp)
|
|
t = NULL;
|
|
}
|
|
attach_shadowed(q, parent, t);
|
|
unlock_mount_hash();
|
|
}
|
|
}
|
|
return res;
|
|
out:
|
|
if (res) {
|
|
lock_mount_hash();
|
|
umount_tree(res, 0);
|
|
unlock_mount_hash();
|
|
}
|
|
return q;
|
|
}
|
|
|
|
/* Caller should check returned pointer for errors */
|
|
|
|
struct vfsmount *collect_mounts(struct path *path)
|
|
{
|
|
struct mount *tree;
|
|
namespace_lock();
|
|
tree = copy_tree(real_mount(path->mnt), path->dentry,
|
|
CL_COPY_ALL | CL_PRIVATE);
|
|
namespace_unlock();
|
|
if (IS_ERR(tree))
|
|
return ERR_CAST(tree);
|
|
return &tree->mnt;
|
|
}
|
|
|
|
void drop_collected_mounts(struct vfsmount *mnt)
|
|
{
|
|
namespace_lock();
|
|
lock_mount_hash();
|
|
umount_tree(real_mount(mnt), 0);
|
|
unlock_mount_hash();
|
|
namespace_unlock();
|
|
}
|
|
|
|
/**
|
|
* clone_private_mount - create a private clone of a path
|
|
*
|
|
* This creates a new vfsmount, which will be the clone of @path. The new will
|
|
* not be attached anywhere in the namespace and will be private (i.e. changes
|
|
* to the originating mount won't be propagated into this).
|
|
*
|
|
* Release with mntput().
|
|
*/
|
|
struct vfsmount *clone_private_mount(struct path *path)
|
|
{
|
|
struct mount *old_mnt = real_mount(path->mnt);
|
|
struct mount *new_mnt;
|
|
|
|
if (IS_MNT_UNBINDABLE(old_mnt))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
down_read(&namespace_sem);
|
|
new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
|
|
up_read(&namespace_sem);
|
|
if (IS_ERR(new_mnt))
|
|
return ERR_CAST(new_mnt);
|
|
|
|
return &new_mnt->mnt;
|
|
}
|
|
EXPORT_SYMBOL_GPL(clone_private_mount);
|
|
|
|
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
|
|
struct vfsmount *root)
|
|
{
|
|
struct mount *mnt;
|
|
int res = f(root, arg);
|
|
if (res)
|
|
return res;
|
|
list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
|
|
res = f(&mnt->mnt, arg);
|
|
if (res)
|
|
return res;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void cleanup_group_ids(struct mount *mnt, struct mount *end)
|
|
{
|
|
struct mount *p;
|
|
|
|
for (p = mnt; p != end; p = next_mnt(p, mnt)) {
|
|
if (p->mnt_group_id && !IS_MNT_SHARED(p))
|
|
mnt_release_group_id(p);
|
|
}
|
|
}
|
|
|
|
static int invent_group_ids(struct mount *mnt, bool recurse)
|
|
{
|
|
struct mount *p;
|
|
|
|
for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
|
|
if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
|
|
int err = mnt_alloc_group_id(p);
|
|
if (err) {
|
|
cleanup_group_ids(mnt, p);
|
|
return err;
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* @source_mnt : mount tree to be attached
|
|
* @nd : place the mount tree @source_mnt is attached
|
|
* @parent_nd : if non-null, detach the source_mnt from its parent and
|
|
* store the parent mount and mountpoint dentry.
|
|
* (done when source_mnt is moved)
|
|
*
|
|
* NOTE: in the table below explains the semantics when a source mount
|
|
* of a given type is attached to a destination mount of a given type.
|
|
* ---------------------------------------------------------------------------
|
|
* | BIND MOUNT OPERATION |
|
|
* |**************************************************************************
|
|
* | source-->| shared | private | slave | unbindable |
|
|
* | dest | | | | |
|
|
* | | | | | | |
|
|
* | v | | | | |
|
|
* |**************************************************************************
|
|
* | shared | shared (++) | shared (+) | shared(+++)| invalid |
|
|
* | | | | | |
|
|
* |non-shared| shared (+) | private | slave (*) | invalid |
|
|
* ***************************************************************************
|
|
* A bind operation clones the source mount and mounts the clone on the
|
|
* destination mount.
|
|
*
|
|
* (++) the cloned mount is propagated to all the mounts in the propagation
|
|
* tree of the destination mount and the cloned mount is added to
|
|
* the peer group of the source mount.
|
|
* (+) the cloned mount is created under the destination mount and is marked
|
|
* as shared. The cloned mount is added to the peer group of the source
|
|
* mount.
|
|
* (+++) the mount is propagated to all the mounts in the propagation tree
|
|
* of the destination mount and the cloned mount is made slave
|
|
* of the same master as that of the source mount. The cloned mount
|
|
* is marked as 'shared and slave'.
|
|
* (*) the cloned mount is made a slave of the same master as that of the
|
|
* source mount.
|
|
*
|
|
* ---------------------------------------------------------------------------
|
|
* | MOVE MOUNT OPERATION |
|
|
* |**************************************************************************
|
|
* | source-->| shared | private | slave | unbindable |
|
|
* | dest | | | | |
|
|
* | | | | | | |
|
|
* | v | | | | |
|
|
* |**************************************************************************
|
|
* | shared | shared (+) | shared (+) | shared(+++) | invalid |
|
|
* | | | | | |
|
|
* |non-shared| shared (+*) | private | slave (*) | unbindable |
|
|
* ***************************************************************************
|
|
*
|
|
* (+) the mount is moved to the destination. And is then propagated to
|
|
* all the mounts in the propagation tree of the destination mount.
|
|
* (+*) the mount is moved to the destination.
|
|
* (+++) the mount is moved to the destination and is then propagated to
|
|
* all the mounts belonging to the destination mount's propagation tree.
|
|
* the mount is marked as 'shared and slave'.
|
|
* (*) the mount continues to be a slave at the new location.
|
|
*
|
|
* if the source mount is a tree, the operations explained above is
|
|
* applied to each mount in the tree.
|
|
* Must be called without spinlocks held, since this function can sleep
|
|
* in allocations.
|
|
*/
|
|
static int attach_recursive_mnt(struct mount *source_mnt,
|
|
struct mount *dest_mnt,
|
|
struct mountpoint *dest_mp,
|
|
struct path *parent_path)
|
|
{
|
|
HLIST_HEAD(tree_list);
|
|
struct mount *child, *p;
|
|
struct hlist_node *n;
|
|
int err;
|
|
|
|
if (IS_MNT_SHARED(dest_mnt)) {
|
|
err = invent_group_ids(source_mnt, true);
|
|
if (err)
|
|
goto out;
|
|
err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
|
|
lock_mount_hash();
|
|
if (err)
|
|
goto out_cleanup_ids;
|
|
for (p = source_mnt; p; p = next_mnt(p, source_mnt))
|
|
set_mnt_shared(p);
|
|
} else {
|
|
lock_mount_hash();
|
|
}
|
|
if (parent_path) {
|
|
detach_mnt(source_mnt, parent_path);
|
|
attach_mnt(source_mnt, dest_mnt, dest_mp);
|
|
touch_mnt_namespace(source_mnt->mnt_ns);
|
|
} else {
|
|
mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
|
|
commit_tree(source_mnt, NULL);
|
|
}
|
|
|
|
hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
|
|
struct mount *q;
|
|
hlist_del_init(&child->mnt_hash);
|
|
q = __lookup_mnt_last(&child->mnt_parent->mnt,
|
|
child->mnt_mountpoint);
|
|
commit_tree(child, q);
|
|
}
|
|
unlock_mount_hash();
|
|
|
|
return 0;
|
|
|
|
out_cleanup_ids:
|
|
while (!hlist_empty(&tree_list)) {
|
|
child = hlist_entry(tree_list.first, struct mount, mnt_hash);
|
|
umount_tree(child, 0);
|
|
}
|
|
unlock_mount_hash();
|
|
cleanup_group_ids(source_mnt, NULL);
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
static struct mountpoint *lock_mount(struct path *path)
|
|
{
|
|
struct vfsmount *mnt;
|
|
struct dentry *dentry = path->dentry;
|
|
retry:
|
|
mutex_lock(&dentry->d_inode->i_mutex);
|
|
if (unlikely(cant_mount(dentry))) {
|
|
mutex_unlock(&dentry->d_inode->i_mutex);
|
|
return ERR_PTR(-ENOENT);
|
|
}
|
|
namespace_lock();
|
|
mnt = lookup_mnt(path);
|
|
if (likely(!mnt)) {
|
|
struct mountpoint *mp = lookup_mountpoint(dentry);
|
|
if (!mp)
|
|
mp = new_mountpoint(dentry);
|
|
if (IS_ERR(mp)) {
|
|
namespace_unlock();
|
|
mutex_unlock(&dentry->d_inode->i_mutex);
|
|
return mp;
|
|
}
|
|
return mp;
|
|
}
|
|
namespace_unlock();
|
|
mutex_unlock(&path->dentry->d_inode->i_mutex);
|
|
path_put(path);
|
|
path->mnt = mnt;
|
|
dentry = path->dentry = dget(mnt->mnt_root);
|
|
goto retry;
|
|
}
|
|
|
|
static void unlock_mount(struct mountpoint *where)
|
|
{
|
|
struct dentry *dentry = where->m_dentry;
|
|
put_mountpoint(where);
|
|
namespace_unlock();
|
|
mutex_unlock(&dentry->d_inode->i_mutex);
|
|
}
|
|
|
|
static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
|
|
{
|
|
if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
|
|
return -EINVAL;
|
|
|
|
if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
|
|
S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
|
|
return -ENOTDIR;
|
|
|
|
return attach_recursive_mnt(mnt, p, mp, NULL);
|
|
}
|
|
|
|
/*
|
|
* Sanity check the flags to change_mnt_propagation.
|
|
*/
|
|
|
|
static int flags_to_propagation_type(int flags)
|
|
{
|
|
int type = flags & ~(MS_REC | MS_SILENT);
|
|
|
|
/* Fail if any non-propagation flags are set */
|
|
if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
|
|
return 0;
|
|
/* Only one propagation flag should be set */
|
|
if (!is_power_of_2(type))
|
|
return 0;
|
|
return type;
|
|
}
|
|
|
|
/*
|
|
* recursively change the type of the mountpoint.
|
|
*/
|
|
static int do_change_type(struct path *path, int flag)
|
|
{
|
|
struct mount *m;
|
|
struct mount *mnt = real_mount(path->mnt);
|
|
int recurse = flag & MS_REC;
|
|
int type;
|
|
int err = 0;
|
|
|
|
if (path->dentry != path->mnt->mnt_root)
|
|
return -EINVAL;
|
|
|
|
type = flags_to_propagation_type(flag);
|
|
if (!type)
|
|
return -EINVAL;
|
|
|
|
namespace_lock();
|
|
if (type == MS_SHARED) {
|
|
err = invent_group_ids(mnt, recurse);
|
|
if (err)
|
|
goto out_unlock;
|
|
}
|
|
|
|
lock_mount_hash();
|
|
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
|
|
change_mnt_propagation(m, type);
|
|
unlock_mount_hash();
|
|
|
|
out_unlock:
|
|
namespace_unlock();
|
|
return err;
|
|
}
|
|
|
|
static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
|
|
{
|
|
struct mount *child;
|
|
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
|
|
if (!is_subdir(child->mnt_mountpoint, dentry))
|
|
continue;
|
|
|
|
if (child->mnt.mnt_flags & MNT_LOCKED)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* do loopback mount.
|
|
*/
|
|
static int do_loopback(struct path *path, const char *old_name,
|
|
int recurse)
|
|
{
|
|
struct path old_path;
|
|
struct mount *mnt = NULL, *old, *parent;
|
|
struct mountpoint *mp;
|
|
int err;
|
|
if (!old_name || !*old_name)
|
|
return -EINVAL;
|
|
err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
|
|
if (err)
|
|
return err;
|
|
|
|
err = -EINVAL;
|
|
if (mnt_ns_loop(old_path.dentry))
|
|
goto out;
|
|
|
|
mp = lock_mount(path);
|
|
err = PTR_ERR(mp);
|
|
if (IS_ERR(mp))
|
|
goto out;
|
|
|
|
old = real_mount(old_path.mnt);
|
|
parent = real_mount(path->mnt);
|
|
|
|
err = -EINVAL;
|
|
if (IS_MNT_UNBINDABLE(old))
|
|
goto out2;
|
|
|
|
if (!check_mnt(parent) || !check_mnt(old))
|
|
goto out2;
|
|
|
|
if (!recurse && has_locked_children(old, old_path.dentry))
|
|
goto out2;
|
|
|
|
if (recurse)
|
|
mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
|
|
else
|
|
mnt = clone_mnt(old, old_path.dentry, 0);
|
|
|
|
if (IS_ERR(mnt)) {
|
|
err = PTR_ERR(mnt);
|
|
goto out2;
|
|
}
|
|
|
|
mnt->mnt.mnt_flags &= ~MNT_LOCKED;
|
|
|
|
err = graft_tree(mnt, parent, mp);
|
|
if (err) {
|
|
lock_mount_hash();
|
|
umount_tree(mnt, 0);
|
|
unlock_mount_hash();
|
|
}
|
|
out2:
|
|
unlock_mount(mp);
|
|
out:
|
|
path_put(&old_path);
|
|
return err;
|
|
}
|
|
|
|
static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
|
|
{
|
|
int error = 0;
|
|
int readonly_request = 0;
|
|
|
|
if (ms_flags & MS_RDONLY)
|
|
readonly_request = 1;
|
|
if (readonly_request == __mnt_is_readonly(mnt))
|
|
return 0;
|
|
|
|
if (readonly_request)
|
|
error = mnt_make_readonly(real_mount(mnt));
|
|
else
|
|
__mnt_unmake_readonly(real_mount(mnt));
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* change filesystem flags. dir should be a physical root of filesystem.
|
|
* If you've mounted a non-root directory somewhere and want to do remount
|
|
* on it - tough luck.
|
|
*/
|
|
static int do_remount(struct path *path, int flags, int mnt_flags,
|
|
void *data)
|
|
{
|
|
int err;
|
|
struct super_block *sb = path->mnt->mnt_sb;
|
|
struct mount *mnt = real_mount(path->mnt);
|
|
|
|
if (!check_mnt(mnt))
|
|
return -EINVAL;
|
|
|
|
if (path->dentry != path->mnt->mnt_root)
|
|
return -EINVAL;
|
|
|
|
/* Don't allow changing of locked mnt flags.
|
|
*
|
|
* No locks need to be held here while testing the various
|
|
* MNT_LOCK flags because those flags can never be cleared
|
|
* once they are set.
|
|
*/
|
|
if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
|
|
!(mnt_flags & MNT_READONLY)) {
|
|
return -EPERM;
|
|
}
|
|
if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
|
|
!(mnt_flags & MNT_NODEV)) {
|
|
/* Was the nodev implicitly added in mount? */
|
|
if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
|
|
!(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
|
|
mnt_flags |= MNT_NODEV;
|
|
} else {
|
|
return -EPERM;
|
|
}
|
|
}
|
|
if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
|
|
!(mnt_flags & MNT_NOSUID)) {
|
|
return -EPERM;
|
|
}
|
|
if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) &&
|
|
!(mnt_flags & MNT_NOEXEC)) {
|
|
return -EPERM;
|
|
}
|
|
if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
|
|
((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) {
|
|
return -EPERM;
|
|
}
|
|
|
|
err = security_sb_remount(sb, data);
|
|
if (err)
|
|
return err;
|
|
|
|
down_write(&sb->s_umount);
|
|
if (flags & MS_BIND)
|
|
err = change_mount_flags(path->mnt, flags);
|
|
else if (!capable(CAP_SYS_ADMIN))
|
|
err = -EPERM;
|
|
else
|
|
err = do_remount_sb(sb, flags, data, 0);
|
|
if (!err) {
|
|
lock_mount_hash();
|
|
mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
|
|
mnt->mnt.mnt_flags = mnt_flags;
|
|
touch_mnt_namespace(mnt->mnt_ns);
|
|
unlock_mount_hash();
|
|
}
|
|
up_write(&sb->s_umount);
|
|
return err;
|
|
}
|
|
|
|
static inline int tree_contains_unbindable(struct mount *mnt)
|
|
{
|
|
struct mount *p;
|
|
for (p = mnt; p; p = next_mnt(p, mnt)) {
|
|
if (IS_MNT_UNBINDABLE(p))
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int do_move_mount(struct path *path, const char *old_name)
|
|
{
|
|
struct path old_path, parent_path;
|
|
struct mount *p;
|
|
struct mount *old;
|
|
struct mountpoint *mp;
|
|
int err;
|
|
if (!old_name || !*old_name)
|
|
return -EINVAL;
|
|
err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
|
|
if (err)
|
|
return err;
|
|
|
|
mp = lock_mount(path);
|
|
err = PTR_ERR(mp);
|
|
if (IS_ERR(mp))
|
|
goto out;
|
|
|
|
old = real_mount(old_path.mnt);
|
|
p = real_mount(path->mnt);
|
|
|
|
err = -EINVAL;
|
|
if (!check_mnt(p) || !check_mnt(old))
|
|
goto out1;
|
|
|
|
if (old->mnt.mnt_flags & MNT_LOCKED)
|
|
goto out1;
|
|
|
|
err = -EINVAL;
|
|
if (old_path.dentry != old_path.mnt->mnt_root)
|
|
goto out1;
|
|
|
|
if (!mnt_has_parent(old))
|
|
goto out1;
|
|
|
|
if (S_ISDIR(path->dentry->d_inode->i_mode) !=
|
|
S_ISDIR(old_path.dentry->d_inode->i_mode))
|
|
goto out1;
|
|
/*
|
|
* Don't move a mount residing in a shared parent.
|
|
*/
|
|
if (IS_MNT_SHARED(old->mnt_parent))
|
|
goto out1;
|
|
/*
|
|
* Don't move a mount tree containing unbindable mounts to a destination
|
|
* mount which is shared.
|
|
*/
|
|
if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
|
|
goto out1;
|
|
err = -ELOOP;
|
|
for (; mnt_has_parent(p); p = p->mnt_parent)
|
|
if (p == old)
|
|
goto out1;
|
|
|
|
err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
|
|
if (err)
|
|
goto out1;
|
|
|
|
/* if the mount is moved, it should no longer be expire
|
|
* automatically */
|
|
list_del_init(&old->mnt_expire);
|
|
out1:
|
|
unlock_mount(mp);
|
|
out:
|
|
if (!err)
|
|
path_put(&parent_path);
|
|
path_put(&old_path);
|
|
return err;
|
|
}
|
|
|
|
static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
|
|
{
|
|
int err;
|
|
const char *subtype = strchr(fstype, '.');
|
|
if (subtype) {
|
|
subtype++;
|
|
err = -EINVAL;
|
|
if (!subtype[0])
|
|
goto err;
|
|
} else
|
|
subtype = "";
|
|
|
|
mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
|
|
err = -ENOMEM;
|
|
if (!mnt->mnt_sb->s_subtype)
|
|
goto err;
|
|
return mnt;
|
|
|
|
err:
|
|
mntput(mnt);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
/*
|
|
* add a mount into a namespace's mount tree
|
|
*/
|
|
static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
|
|
{
|
|
struct mountpoint *mp;
|
|
struct mount *parent;
|
|
int err;
|
|
|
|
mnt_flags &= ~MNT_INTERNAL_FLAGS;
|
|
|
|
mp = lock_mount(path);
|
|
if (IS_ERR(mp))
|
|
return PTR_ERR(mp);
|
|
|
|
parent = real_mount(path->mnt);
|
|
err = -EINVAL;
|
|
if (unlikely(!check_mnt(parent))) {
|
|
/* that's acceptable only for automounts done in private ns */
|
|
if (!(mnt_flags & MNT_SHRINKABLE))
|
|
goto unlock;
|
|
/* ... and for those we'd better have mountpoint still alive */
|
|
if (!parent->mnt_ns)
|
|
goto unlock;
|
|
}
|
|
|
|
/* Refuse the same filesystem on the same mount point */
|
|
err = -EBUSY;
|
|
if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
|
|
path->mnt->mnt_root == path->dentry)
|
|
goto unlock;
|
|
|
|
err = -EINVAL;
|
|
if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
|
|
goto unlock;
|
|
|
|
newmnt->mnt.mnt_flags = mnt_flags;
|
|
err = graft_tree(newmnt, parent, mp);
|
|
|
|
unlock:
|
|
unlock_mount(mp);
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* create a new mount for userspace and request it to be added into the
|
|
* namespace's tree
|
|
*/
|
|
static int do_new_mount(struct path *path, const char *fstype, int flags,
|
|
int mnt_flags, const char *name, void *data)
|
|
{
|
|
struct file_system_type *type;
|
|
struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
|
|
struct vfsmount *mnt;
|
|
int err;
|
|
|
|
if (!fstype)
|
|
return -EINVAL;
|
|
|
|
type = get_fs_type(fstype);
|
|
if (!type)
|
|
return -ENODEV;
|
|
|
|
if (user_ns != &init_user_ns) {
|
|
if (!(type->fs_flags & FS_USERNS_MOUNT)) {
|
|
put_filesystem(type);
|
|
return -EPERM;
|
|
}
|
|
/* Only in special cases allow devices from mounts
|
|
* created outside the initial user namespace.
|
|
*/
|
|
if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
|
|
flags |= MS_NODEV;
|
|
mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
|
|
}
|
|
}
|
|
|
|
mnt = vfs_kern_mount(type, flags, name, data);
|
|
if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
|
|
!mnt->mnt_sb->s_subtype)
|
|
mnt = fs_set_subtype(mnt, fstype);
|
|
|
|
put_filesystem(type);
|
|
if (IS_ERR(mnt))
|
|
return PTR_ERR(mnt);
|
|
|
|
err = do_add_mount(real_mount(mnt), path, mnt_flags);
|
|
if (err)
|
|
mntput(mnt);
|
|
return err;
|
|
}
|
|
|
|
int finish_automount(struct vfsmount *m, struct path *path)
|
|
{
|
|
struct mount *mnt = real_mount(m);
|
|
int err;
|
|
/* The new mount record should have at least 2 refs to prevent it being
|
|
* expired before we get a chance to add it
|
|
*/
|
|
BUG_ON(mnt_get_count(mnt) < 2);
|
|
|
|
if (m->mnt_sb == path->mnt->mnt_sb &&
|
|
m->mnt_root == path->dentry) {
|
|
err = -ELOOP;
|
|
goto fail;
|
|
}
|
|
|
|
err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
|
|
if (!err)
|
|
return 0;
|
|
fail:
|
|
/* remove m from any expiration list it may be on */
|
|
if (!list_empty(&mnt->mnt_expire)) {
|
|
namespace_lock();
|
|
list_del_init(&mnt->mnt_expire);
|
|
namespace_unlock();
|
|
}
|
|
mntput(m);
|
|
mntput(m);
|
|
return err;
|
|
}
|
|
|
|
/**
|
|
* mnt_set_expiry - Put a mount on an expiration list
|
|
* @mnt: The mount to list.
|
|
* @expiry_list: The list to add the mount to.
|
|
*/
|
|
void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
|
|
{
|
|
namespace_lock();
|
|
|
|
list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
|
|
|
|
namespace_unlock();
|
|
}
|
|
EXPORT_SYMBOL(mnt_set_expiry);
|
|
|
|
/*
|
|
* process a list of expirable mountpoints with the intent of discarding any
|
|
* mountpoints that aren't in use and haven't been touched since last we came
|
|
* here
|
|
*/
|
|
void mark_mounts_for_expiry(struct list_head *mounts)
|
|
{
|
|
struct mount *mnt, *next;
|
|
LIST_HEAD(graveyard);
|
|
|
|
if (list_empty(mounts))
|
|
return;
|
|
|
|
namespace_lock();
|
|
lock_mount_hash();
|
|
|
|
/* extract from the expiration list every vfsmount that matches the
|
|
* following criteria:
|
|
* - only referenced by its parent vfsmount
|
|
* - still marked for expiry (marked on the last call here; marks are
|
|
* cleared by mntput())
|
|
*/
|
|
list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
|
|
if (!xchg(&mnt->mnt_expiry_mark, 1) ||
|
|
propagate_mount_busy(mnt, 1))
|
|
continue;
|
|
list_move(&mnt->mnt_expire, &graveyard);
|
|
}
|
|
while (!list_empty(&graveyard)) {
|
|
mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
|
|
touch_mnt_namespace(mnt->mnt_ns);
|
|
umount_tree(mnt, 1);
|
|
}
|
|
unlock_mount_hash();
|
|
namespace_unlock();
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
|
|
|
|
/*
|
|
* Ripoff of 'select_parent()'
|
|
*
|
|
* search the list of submounts for a given mountpoint, and move any
|
|
* shrinkable submounts to the 'graveyard' list.
|
|
*/
|
|
static int select_submounts(struct mount *parent, struct list_head *graveyard)
|
|
{
|
|
struct mount *this_parent = parent;
|
|
struct list_head *next;
|
|
int found = 0;
|
|
|
|
repeat:
|
|
next = this_parent->mnt_mounts.next;
|
|
resume:
|
|
while (next != &this_parent->mnt_mounts) {
|
|
struct list_head *tmp = next;
|
|
struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
|
|
|
|
next = tmp->next;
|
|
if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
|
|
continue;
|
|
/*
|
|
* Descend a level if the d_mounts list is non-empty.
|
|
*/
|
|
if (!list_empty(&mnt->mnt_mounts)) {
|
|
this_parent = mnt;
|
|
goto repeat;
|
|
}
|
|
|
|
if (!propagate_mount_busy(mnt, 1)) {
|
|
list_move_tail(&mnt->mnt_expire, graveyard);
|
|
found++;
|
|
}
|
|
}
|
|
/*
|
|
* All done at this level ... ascend and resume the search
|
|
*/
|
|
if (this_parent != parent) {
|
|
next = this_parent->mnt_child.next;
|
|
this_parent = this_parent->mnt_parent;
|
|
goto resume;
|
|
}
|
|
return found;
|
|
}
|
|
|
|
/*
|
|
* process a list of expirable mountpoints with the intent of discarding any
|
|
* submounts of a specific parent mountpoint
|
|
*
|
|
* mount_lock must be held for write
|
|
*/
|
|
static void shrink_submounts(struct mount *mnt)
|
|
{
|
|
LIST_HEAD(graveyard);
|
|
struct mount *m;
|
|
|
|
/* extract submounts of 'mountpoint' from the expiration list */
|
|
while (select_submounts(mnt, &graveyard)) {
|
|
while (!list_empty(&graveyard)) {
|
|
m = list_first_entry(&graveyard, struct mount,
|
|
mnt_expire);
|
|
touch_mnt_namespace(m->mnt_ns);
|
|
umount_tree(m, 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Some copy_from_user() implementations do not return the exact number of
|
|
* bytes remaining to copy on a fault. But copy_mount_options() requires that.
|
|
* Note that this function differs from copy_from_user() in that it will oops
|
|
* on bad values of `to', rather than returning a short copy.
|
|
*/
|
|
static long exact_copy_from_user(void *to, const void __user * from,
|
|
unsigned long n)
|
|
{
|
|
char *t = to;
|
|
const char __user *f = from;
|
|
char c;
|
|
|
|
if (!access_ok(VERIFY_READ, from, n))
|
|
return n;
|
|
|
|
while (n) {
|
|
if (__get_user(c, f)) {
|
|
memset(t, 0, n);
|
|
break;
|
|
}
|
|
*t++ = c;
|
|
f++;
|
|
n--;
|
|
}
|
|
return n;
|
|
}
|
|
|
|
int copy_mount_options(const void __user * data, unsigned long *where)
|
|
{
|
|
int i;
|
|
unsigned long page;
|
|
unsigned long size;
|
|
|
|
*where = 0;
|
|
if (!data)
|
|
return 0;
|
|
|
|
if (!(page = __get_free_page(GFP_KERNEL)))
|
|
return -ENOMEM;
|
|
|
|
/* We only care that *some* data at the address the user
|
|
* gave us is valid. Just in case, we'll zero
|
|
* the remainder of the page.
|
|
*/
|
|
/* copy_from_user cannot cross TASK_SIZE ! */
|
|
size = TASK_SIZE - (unsigned long)data;
|
|
if (size > PAGE_SIZE)
|
|
size = PAGE_SIZE;
|
|
|
|
i = size - exact_copy_from_user((void *)page, data, size);
|
|
if (!i) {
|
|
free_page(page);
|
|
return -EFAULT;
|
|
}
|
|
if (i != PAGE_SIZE)
|
|
memset((char *)page + i, 0, PAGE_SIZE - i);
|
|
*where = page;
|
|
return 0;
|
|
}
|
|
|
|
char *copy_mount_string(const void __user *data)
|
|
{
|
|
return data ? strndup_user(data, PAGE_SIZE) : NULL;
|
|
}
|
|
|
|
/*
|
|
* Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
|
|
* be given to the mount() call (ie: read-only, no-dev, no-suid etc).
|
|
*
|
|
* data is a (void *) that can point to any structure up to
|
|
* PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
|
|
* information (or be NULL).
|
|
*
|
|
* Pre-0.97 versions of mount() didn't have a flags word.
|
|
* When the flags word was introduced its top half was required
|
|
* to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
|
|
* Therefore, if this magic number is present, it carries no information
|
|
* and must be discarded.
|
|
*/
|
|
long do_mount(const char *dev_name, const char __user *dir_name,
|
|
const char *type_page, unsigned long flags, void *data_page)
|
|
{
|
|
struct path path;
|
|
int retval = 0;
|
|
int mnt_flags = 0;
|
|
|
|
/* Discard magic */
|
|
if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
|
|
flags &= ~MS_MGC_MSK;
|
|
|
|
/* Basic sanity checks */
|
|
if (data_page)
|
|
((char *)data_page)[PAGE_SIZE - 1] = 0;
|
|
|
|
/* ... and get the mountpoint */
|
|
retval = user_path(dir_name, &path);
|
|
if (retval)
|
|
return retval;
|
|
|
|
retval = security_sb_mount(dev_name, &path,
|
|
type_page, flags, data_page);
|
|
if (!retval && !may_mount())
|
|
retval = -EPERM;
|
|
if (retval)
|
|
goto dput_out;
|
|
|
|
/* Default to relatime unless overriden */
|
|
if (!(flags & MS_NOATIME))
|
|
mnt_flags |= MNT_RELATIME;
|
|
|
|
/* Separate the per-mountpoint flags */
|
|
if (flags & MS_NOSUID)
|
|
mnt_flags |= MNT_NOSUID;
|
|
if (flags & MS_NODEV)
|
|
mnt_flags |= MNT_NODEV;
|
|
if (flags & MS_NOEXEC)
|
|
mnt_flags |= MNT_NOEXEC;
|
|
if (flags & MS_NOATIME)
|
|
mnt_flags |= MNT_NOATIME;
|
|
if (flags & MS_NODIRATIME)
|
|
mnt_flags |= MNT_NODIRATIME;
|
|
if (flags & MS_STRICTATIME)
|
|
mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
|
|
if (flags & MS_RDONLY)
|
|
mnt_flags |= MNT_READONLY;
|
|
|
|
/* The default atime for remount is preservation */
|
|
if ((flags & MS_REMOUNT) &&
|
|
((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
|
|
MS_STRICTATIME)) == 0)) {
|
|
mnt_flags &= ~MNT_ATIME_MASK;
|
|
mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK;
|
|
}
|
|
|
|
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
|
|
MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
|
|
MS_STRICTATIME);
|
|
|
|
if (flags & MS_REMOUNT)
|
|
retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
|
|
data_page);
|
|
else if (flags & MS_BIND)
|
|
retval = do_loopback(&path, dev_name, flags & MS_REC);
|
|
else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
|
|
retval = do_change_type(&path, flags);
|
|
else if (flags & MS_MOVE)
|
|
retval = do_move_mount(&path, dev_name);
|
|
else
|
|
retval = do_new_mount(&path, type_page, flags, mnt_flags,
|
|
dev_name, data_page);
|
|
dput_out:
|
|
path_put(&path);
|
|
return retval;
|
|
}
|
|
|
|
static void free_mnt_ns(struct mnt_namespace *ns)
|
|
{
|
|
proc_free_inum(ns->proc_inum);
|
|
put_user_ns(ns->user_ns);
|
|
kfree(ns);
|
|
}
|
|
|
|
/*
|
|
* Assign a sequence number so we can detect when we attempt to bind
|
|
* mount a reference to an older mount namespace into the current
|
|
* mount namespace, preventing reference counting loops. A 64bit
|
|
* number incrementing at 10Ghz will take 12,427 years to wrap which
|
|
* is effectively never, so we can ignore the possibility.
|
|
*/
|
|
static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
|
|
|
|
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
|
|
{
|
|
struct mnt_namespace *new_ns;
|
|
int ret;
|
|
|
|
new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
|
|
if (!new_ns)
|
|
return ERR_PTR(-ENOMEM);
|
|
ret = proc_alloc_inum(&new_ns->proc_inum);
|
|
if (ret) {
|
|
kfree(new_ns);
|
|
return ERR_PTR(ret);
|
|
}
|
|
new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
|
|
atomic_set(&new_ns->count, 1);
|
|
new_ns->root = NULL;
|
|
INIT_LIST_HEAD(&new_ns->list);
|
|
init_waitqueue_head(&new_ns->poll);
|
|
new_ns->event = 0;
|
|
new_ns->user_ns = get_user_ns(user_ns);
|
|
return new_ns;
|
|
}
|
|
|
|
struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
|
|
struct user_namespace *user_ns, struct fs_struct *new_fs)
|
|
{
|
|
struct mnt_namespace *new_ns;
|
|
struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
|
|
struct mount *p, *q;
|
|
struct mount *old;
|
|
struct mount *new;
|
|
int copy_flags;
|
|
|
|
BUG_ON(!ns);
|
|
|
|
if (likely(!(flags & CLONE_NEWNS))) {
|
|
get_mnt_ns(ns);
|
|
return ns;
|
|
}
|
|
|
|
old = ns->root;
|
|
|
|
new_ns = alloc_mnt_ns(user_ns);
|
|
if (IS_ERR(new_ns))
|
|
return new_ns;
|
|
|
|
namespace_lock();
|
|
/* First pass: copy the tree topology */
|
|
copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
|
|
if (user_ns != ns->user_ns)
|
|
copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
|
|
new = copy_tree(old, old->mnt.mnt_root, copy_flags);
|
|
if (IS_ERR(new)) {
|
|
namespace_unlock();
|
|
free_mnt_ns(new_ns);
|
|
return ERR_CAST(new);
|
|
}
|
|
new_ns->root = new;
|
|
list_add_tail(&new_ns->list, &new->mnt_list);
|
|
|
|
/*
|
|
* Second pass: switch the tsk->fs->* elements and mark new vfsmounts
|
|
* as belonging to new namespace. We have already acquired a private
|
|
* fs_struct, so tsk->fs->lock is not needed.
|
|
*/
|
|
p = old;
|
|
q = new;
|
|
while (p) {
|
|
q->mnt_ns = new_ns;
|
|
if (new_fs) {
|
|
if (&p->mnt == new_fs->root.mnt) {
|
|
new_fs->root.mnt = mntget(&q->mnt);
|
|
rootmnt = &p->mnt;
|
|
}
|
|
if (&p->mnt == new_fs->pwd.mnt) {
|
|
new_fs->pwd.mnt = mntget(&q->mnt);
|
|
pwdmnt = &p->mnt;
|
|
}
|
|
}
|
|
p = next_mnt(p, old);
|
|
q = next_mnt(q, new);
|
|
if (!q)
|
|
break;
|
|
while (p->mnt.mnt_root != q->mnt.mnt_root)
|
|
p = next_mnt(p, old);
|
|
}
|
|
namespace_unlock();
|
|
|
|
if (rootmnt)
|
|
mntput(rootmnt);
|
|
if (pwdmnt)
|
|
mntput(pwdmnt);
|
|
|
|
return new_ns;
|
|
}
|
|
|
|
/**
|
|
* create_mnt_ns - creates a private namespace and adds a root filesystem
|
|
* @mnt: pointer to the new root filesystem mountpoint
|
|
*/
|
|
static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
|
|
{
|
|
struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
|
|
if (!IS_ERR(new_ns)) {
|
|
struct mount *mnt = real_mount(m);
|
|
mnt->mnt_ns = new_ns;
|
|
new_ns->root = mnt;
|
|
list_add(&mnt->mnt_list, &new_ns->list);
|
|
} else {
|
|
mntput(m);
|
|
}
|
|
return new_ns;
|
|
}
|
|
|
|
struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
|
|
{
|
|
struct mnt_namespace *ns;
|
|
struct super_block *s;
|
|
struct path path;
|
|
int err;
|
|
|
|
ns = create_mnt_ns(mnt);
|
|
if (IS_ERR(ns))
|
|
return ERR_CAST(ns);
|
|
|
|
err = vfs_path_lookup(mnt->mnt_root, mnt,
|
|
name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
|
|
|
|
put_mnt_ns(ns);
|
|
|
|
if (err)
|
|
return ERR_PTR(err);
|
|
|
|
/* trade a vfsmount reference for active sb one */
|
|
s = path.mnt->mnt_sb;
|
|
atomic_inc(&s->s_active);
|
|
mntput(path.mnt);
|
|
/* lock the sucker */
|
|
down_write(&s->s_umount);
|
|
/* ... and return the root of (sub)tree on it */
|
|
return path.dentry;
|
|
}
|
|
EXPORT_SYMBOL(mount_subtree);
|
|
|
|
SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
|
|
char __user *, type, unsigned long, flags, void __user *, data)
|
|
{
|
|
int ret;
|
|
char *kernel_type;
|
|
char *kernel_dev;
|
|
unsigned long data_page;
|
|
|
|
kernel_type = copy_mount_string(type);
|
|
ret = PTR_ERR(kernel_type);
|
|
if (IS_ERR(kernel_type))
|
|
goto out_type;
|
|
|
|
kernel_dev = copy_mount_string(dev_name);
|
|
ret = PTR_ERR(kernel_dev);
|
|
if (IS_ERR(kernel_dev))
|
|
goto out_dev;
|
|
|
|
ret = copy_mount_options(data, &data_page);
|
|
if (ret < 0)
|
|
goto out_data;
|
|
|
|
ret = do_mount(kernel_dev, dir_name, kernel_type, flags,
|
|
(void *) data_page);
|
|
|
|
free_page(data_page);
|
|
out_data:
|
|
kfree(kernel_dev);
|
|
out_dev:
|
|
kfree(kernel_type);
|
|
out_type:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Return true if path is reachable from root
|
|
*
|
|
* namespace_sem or mount_lock is held
|
|
*/
|
|
bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
|
|
const struct path *root)
|
|
{
|
|
while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
|
|
dentry = mnt->mnt_mountpoint;
|
|
mnt = mnt->mnt_parent;
|
|
}
|
|
return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
|
|
}
|
|
|
|
int path_is_under(struct path *path1, struct path *path2)
|
|
{
|
|
int res;
|
|
read_seqlock_excl(&mount_lock);
|
|
res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
|
|
read_sequnlock_excl(&mount_lock);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(path_is_under);
|
|
|
|
/*
|
|
* pivot_root Semantics:
|
|
* Moves the root file system of the current process to the directory put_old,
|
|
* makes new_root as the new root file system of the current process, and sets
|
|
* root/cwd of all processes which had them on the current root to new_root.
|
|
*
|
|
* Restrictions:
|
|
* The new_root and put_old must be directories, and must not be on the
|
|
* same file system as the current process root. The put_old must be
|
|
* underneath new_root, i.e. adding a non-zero number of /.. to the string
|
|
* pointed to by put_old must yield the same directory as new_root. No other
|
|
* file system may be mounted on put_old. After all, new_root is a mountpoint.
|
|
*
|
|
* Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
|
|
* See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
|
|
* in this situation.
|
|
*
|
|
* Notes:
|
|
* - we don't move root/cwd if they are not at the root (reason: if something
|
|
* cared enough to change them, it's probably wrong to force them elsewhere)
|
|
* - it's okay to pick a root that isn't the root of a file system, e.g.
|
|
* /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
|
|
* though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
|
|
* first.
|
|
*/
|
|
SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
|
|
const char __user *, put_old)
|
|
{
|
|
struct path new, old, parent_path, root_parent, root;
|
|
struct mount *new_mnt, *root_mnt, *old_mnt;
|
|
struct mountpoint *old_mp, *root_mp;
|
|
int error;
|
|
|
|
if (!may_mount())
|
|
return -EPERM;
|
|
|
|
error = user_path_dir(new_root, &new);
|
|
if (error)
|
|
goto out0;
|
|
|
|
error = user_path_dir(put_old, &old);
|
|
if (error)
|
|
goto out1;
|
|
|
|
error = security_sb_pivotroot(&old, &new);
|
|
if (error)
|
|
goto out2;
|
|
|
|
get_fs_root(current->fs, &root);
|
|
old_mp = lock_mount(&old);
|
|
error = PTR_ERR(old_mp);
|
|
if (IS_ERR(old_mp))
|
|
goto out3;
|
|
|
|
error = -EINVAL;
|
|
new_mnt = real_mount(new.mnt);
|
|
root_mnt = real_mount(root.mnt);
|
|
old_mnt = real_mount(old.mnt);
|
|
if (IS_MNT_SHARED(old_mnt) ||
|
|
IS_MNT_SHARED(new_mnt->mnt_parent) ||
|
|
IS_MNT_SHARED(root_mnt->mnt_parent))
|
|
goto out4;
|
|
if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
|
|
goto out4;
|
|
if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
|
|
goto out4;
|
|
error = -ENOENT;
|
|
if (d_unlinked(new.dentry))
|
|
goto out4;
|
|
error = -EBUSY;
|
|
if (new_mnt == root_mnt || old_mnt == root_mnt)
|
|
goto out4; /* loop, on the same file system */
|
|
error = -EINVAL;
|
|
if (root.mnt->mnt_root != root.dentry)
|
|
goto out4; /* not a mountpoint */
|
|
if (!mnt_has_parent(root_mnt))
|
|
goto out4; /* not attached */
|
|
root_mp = root_mnt->mnt_mp;
|
|
if (new.mnt->mnt_root != new.dentry)
|
|
goto out4; /* not a mountpoint */
|
|
if (!mnt_has_parent(new_mnt))
|
|
goto out4; /* not attached */
|
|
/* make sure we can reach put_old from new_root */
|
|
if (!is_path_reachable(old_mnt, old.dentry, &new))
|
|
goto out4;
|
|
/* make certain new is below the root */
|
|
if (!is_path_reachable(new_mnt, new.dentry, &root))
|
|
goto out4;
|
|
root_mp->m_count++; /* pin it so it won't go away */
|
|
lock_mount_hash();
|
|
detach_mnt(new_mnt, &parent_path);
|
|
detach_mnt(root_mnt, &root_parent);
|
|
if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
|
|
new_mnt->mnt.mnt_flags |= MNT_LOCKED;
|
|
root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
|
|
}
|
|
/* mount old root on put_old */
|
|
attach_mnt(root_mnt, old_mnt, old_mp);
|
|
/* mount new_root on / */
|
|
attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
|
|
touch_mnt_namespace(current->nsproxy->mnt_ns);
|
|
unlock_mount_hash();
|
|
chroot_fs_refs(&root, &new);
|
|
put_mountpoint(root_mp);
|
|
error = 0;
|
|
out4:
|
|
unlock_mount(old_mp);
|
|
if (!error) {
|
|
path_put(&root_parent);
|
|
path_put(&parent_path);
|
|
}
|
|
out3:
|
|
path_put(&root);
|
|
out2:
|
|
path_put(&old);
|
|
out1:
|
|
path_put(&new);
|
|
out0:
|
|
return error;
|
|
}
|
|
|
|
static void __init init_mount_tree(void)
|
|
{
|
|
struct vfsmount *mnt;
|
|
struct mnt_namespace *ns;
|
|
struct path root;
|
|
struct file_system_type *type;
|
|
|
|
type = get_fs_type("rootfs");
|
|
if (!type)
|
|
panic("Can't find rootfs type");
|
|
mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
|
|
put_filesystem(type);
|
|
if (IS_ERR(mnt))
|
|
panic("Can't create rootfs");
|
|
|
|
ns = create_mnt_ns(mnt);
|
|
if (IS_ERR(ns))
|
|
panic("Can't allocate initial namespace");
|
|
|
|
init_task.nsproxy->mnt_ns = ns;
|
|
get_mnt_ns(ns);
|
|
|
|
root.mnt = mnt;
|
|
root.dentry = mnt->mnt_root;
|
|
mnt->mnt_flags |= MNT_LOCKED;
|
|
|
|
set_fs_pwd(current->fs, &root);
|
|
set_fs_root(current->fs, &root);
|
|
}
|
|
|
|
void __init mnt_init(void)
|
|
{
|
|
unsigned u;
|
|
int err;
|
|
|
|
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
|
|
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
|
|
|
|
mount_hashtable = alloc_large_system_hash("Mount-cache",
|
|
sizeof(struct hlist_head),
|
|
mhash_entries, 19,
|
|
0,
|
|
&m_hash_shift, &m_hash_mask, 0, 0);
|
|
mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
|
|
sizeof(struct hlist_head),
|
|
mphash_entries, 19,
|
|
0,
|
|
&mp_hash_shift, &mp_hash_mask, 0, 0);
|
|
|
|
if (!mount_hashtable || !mountpoint_hashtable)
|
|
panic("Failed to allocate mount hash table\n");
|
|
|
|
for (u = 0; u <= m_hash_mask; u++)
|
|
INIT_HLIST_HEAD(&mount_hashtable[u]);
|
|
for (u = 0; u <= mp_hash_mask; u++)
|
|
INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
|
|
|
|
kernfs_init();
|
|
|
|
err = sysfs_init();
|
|
if (err)
|
|
printk(KERN_WARNING "%s: sysfs_init error: %d\n",
|
|
__func__, err);
|
|
fs_kobj = kobject_create_and_add("fs", NULL);
|
|
if (!fs_kobj)
|
|
printk(KERN_WARNING "%s: kobj create error\n", __func__);
|
|
init_rootfs();
|
|
init_mount_tree();
|
|
}
|
|
|
|
void put_mnt_ns(struct mnt_namespace *ns)
|
|
{
|
|
if (!atomic_dec_and_test(&ns->count))
|
|
return;
|
|
drop_collected_mounts(&ns->root->mnt);
|
|
free_mnt_ns(ns);
|
|
}
|
|
|
|
struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
|
|
{
|
|
struct vfsmount *mnt;
|
|
mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
|
|
if (!IS_ERR(mnt)) {
|
|
/*
|
|
* it is a longterm mount, don't release mnt until
|
|
* we unmount before file sys is unregistered
|
|
*/
|
|
real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
|
|
}
|
|
return mnt;
|
|
}
|
|
EXPORT_SYMBOL_GPL(kern_mount_data);
|
|
|
|
void kern_unmount(struct vfsmount *mnt)
|
|
{
|
|
/* release long term mount so mount point can be released */
|
|
if (!IS_ERR_OR_NULL(mnt)) {
|
|
real_mount(mnt)->mnt_ns = NULL;
|
|
synchronize_rcu(); /* yecchhh... */
|
|
mntput(mnt);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(kern_unmount);
|
|
|
|
bool our_mnt(struct vfsmount *mnt)
|
|
{
|
|
return check_mnt(real_mount(mnt));
|
|
}
|
|
|
|
bool current_chrooted(void)
|
|
{
|
|
/* Does the current process have a non-standard root */
|
|
struct path ns_root;
|
|
struct path fs_root;
|
|
bool chrooted;
|
|
|
|
/* Find the namespace root */
|
|
ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
|
|
ns_root.dentry = ns_root.mnt->mnt_root;
|
|
path_get(&ns_root);
|
|
while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
|
|
;
|
|
|
|
get_fs_root(current->fs, &fs_root);
|
|
|
|
chrooted = !path_equal(&fs_root, &ns_root);
|
|
|
|
path_put(&fs_root);
|
|
path_put(&ns_root);
|
|
|
|
return chrooted;
|
|
}
|
|
|
|
bool fs_fully_visible(struct file_system_type *type)
|
|
{
|
|
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
|
|
struct mount *mnt;
|
|
bool visible = false;
|
|
|
|
if (unlikely(!ns))
|
|
return false;
|
|
|
|
down_read(&namespace_sem);
|
|
list_for_each_entry(mnt, &ns->list, mnt_list) {
|
|
struct mount *child;
|
|
if (mnt->mnt.mnt_sb->s_type != type)
|
|
continue;
|
|
|
|
/* This mount is not fully visible if there are any child mounts
|
|
* that cover anything except for empty directories.
|
|
*/
|
|
list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
|
|
struct inode *inode = child->mnt_mountpoint->d_inode;
|
|
if (!S_ISDIR(inode->i_mode))
|
|
goto next;
|
|
if (inode->i_nlink > 2)
|
|
goto next;
|
|
}
|
|
visible = true;
|
|
goto found;
|
|
next: ;
|
|
}
|
|
found:
|
|
up_read(&namespace_sem);
|
|
return visible;
|
|
}
|
|
|
|
static void *mntns_get(struct task_struct *task)
|
|
{
|
|
struct mnt_namespace *ns = NULL;
|
|
struct nsproxy *nsproxy;
|
|
|
|
task_lock(task);
|
|
nsproxy = task->nsproxy;
|
|
if (nsproxy) {
|
|
ns = nsproxy->mnt_ns;
|
|
get_mnt_ns(ns);
|
|
}
|
|
task_unlock(task);
|
|
|
|
return ns;
|
|
}
|
|
|
|
static void mntns_put(void *ns)
|
|
{
|
|
put_mnt_ns(ns);
|
|
}
|
|
|
|
static int mntns_install(struct nsproxy *nsproxy, void *ns)
|
|
{
|
|
struct fs_struct *fs = current->fs;
|
|
struct mnt_namespace *mnt_ns = ns;
|
|
struct path root;
|
|
|
|
if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
|
|
!ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
|
|
!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
|
|
if (fs->users != 1)
|
|
return -EINVAL;
|
|
|
|
get_mnt_ns(mnt_ns);
|
|
put_mnt_ns(nsproxy->mnt_ns);
|
|
nsproxy->mnt_ns = mnt_ns;
|
|
|
|
/* Find the root */
|
|
root.mnt = &mnt_ns->root->mnt;
|
|
root.dentry = mnt_ns->root->mnt.mnt_root;
|
|
path_get(&root);
|
|
while(d_mountpoint(root.dentry) && follow_down_one(&root))
|
|
;
|
|
|
|
/* Update the pwd and root */
|
|
set_fs_pwd(fs, &root);
|
|
set_fs_root(fs, &root);
|
|
|
|
path_put(&root);
|
|
return 0;
|
|
}
|
|
|
|
static unsigned int mntns_inum(void *ns)
|
|
{
|
|
struct mnt_namespace *mnt_ns = ns;
|
|
return mnt_ns->proc_inum;
|
|
}
|
|
|
|
const struct proc_ns_operations mntns_operations = {
|
|
.name = "mnt",
|
|
.type = CLONE_NEWNS,
|
|
.get = mntns_get,
|
|
.put = mntns_put,
|
|
.install = mntns_install,
|
|
.inum = mntns_inum,
|
|
};
|