/* * linux/fs/namespace.c * * (C) Copyright Al Viro 2000, 2001 * Released under GPL v2. * * Based on code from fs/super.c, copyright Linus Torvalds and others. * Heavily rewritten. */ #include <linux/syscalls.h> #include <linux/slab.h> #include <linux/sched.h> #include <linux/smp_lock.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/acct.h> #include <linux/capability.h> #include <linux/cpumask.h> #include <linux/module.h> #include <linux/sysfs.h> #include <linux/seq_file.h> #include <linux/mnt_namespace.h> #include <linux/namei.h> #include <linux/nsproxy.h> #include <linux/security.h> #include <linux/mount.h> #include <linux/ramfs.h> #include <linux/log2.h> #include <linux/idr.h> #include <linux/fs_struct.h> #include <asm/uaccess.h> #include <asm/unistd.h> #include "pnode.h" #include "internal.h" #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) #define HASH_SIZE (1UL << HASH_SHIFT) /* spinlock for vfsmount related operations, inplace of dcache_lock */ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); static int event; static DEFINE_IDA(mnt_id_ida); static DEFINE_IDA(mnt_group_ida); static int mnt_id_start = 0; static int mnt_group_start = 1; static struct list_head *mount_hashtable __read_mostly; static struct kmem_cache *mnt_cache __read_mostly; static struct rw_semaphore namespace_sem; /* /sys/fs */ struct kobject *fs_kobj; EXPORT_SYMBOL_GPL(fs_kobj); static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) { unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); tmp += ((unsigned long)dentry / L1_CACHE_BYTES); tmp = tmp + (tmp >> HASH_SHIFT); return tmp & (HASH_SIZE - 1); } #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) /* allocation is serialized by namespace_sem */ static int mnt_alloc_id(struct vfsmount *mnt) { int res; retry: ida_pre_get(&mnt_id_ida, GFP_KERNEL); spin_lock(&vfsmount_lock); res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); if (!res) mnt_id_start = mnt->mnt_id + 1; spin_unlock(&vfsmount_lock); if (res == -EAGAIN) goto retry; return res; } static void mnt_free_id(struct vfsmount *mnt) { int id = mnt->mnt_id; spin_lock(&vfsmount_lock); ida_remove(&mnt_id_ida, id); if (mnt_id_start > id) mnt_id_start = id; spin_unlock(&vfsmount_lock); } /* * Allocate a new peer group ID * * mnt_group_ida is protected by namespace_sem */ static int mnt_alloc_group_id(struct vfsmount *mnt) { int res; if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) return -ENOMEM; res = ida_get_new_above(&mnt_group_ida, mnt_group_start, &mnt->mnt_group_id); if (!res) mnt_group_start = mnt->mnt_group_id + 1; return res; } /* * Release a peer group ID */ void mnt_release_group_id(struct vfsmount *mnt) { int id = mnt->mnt_group_id; ida_remove(&mnt_group_ida, id); if (mnt_group_start > id) mnt_group_start = id; mnt->mnt_group_id = 0; } struct vfsmount *alloc_vfsmnt(const char *name) { struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); if (mnt) { int err; err = mnt_alloc_id(mnt); if (err) goto out_free_cache; if (name) { mnt->mnt_devname = kstrdup(name, GFP_KERNEL); if (!mnt->mnt_devname) goto out_free_id; } atomic_set(&mnt->mnt_count, 1); INIT_LIST_HEAD(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); INIT_LIST_HEAD(&mnt->mnt_mounts); INIT_LIST_HEAD(&mnt->mnt_list); INIT_LIST_HEAD(&mnt->mnt_expire); INIT_LIST_HEAD(&mnt->mnt_share); INIT_LIST_HEAD(&mnt->mnt_slave_list); INIT_LIST_HEAD(&mnt->mnt_slave); #ifdef CONFIG_SMP mnt->mnt_writers = alloc_percpu(int); if (!mnt->mnt_writers) goto out_free_devname; #else mnt->mnt_writers = 0; #endif } return mnt; #ifdef CONFIG_SMP out_free_devname: kfree(mnt->mnt_devname); #endif out_free_id: mnt_free_id(mnt); out_free_cache: kmem_cache_free(mnt_cache, mnt); return NULL; } /* * Most r/o checks on a fs are for operations that take * discrete amounts of time, like a write() or unlink(). * We must keep track of when those operations start * (for permission checks) and when they end, so that * we can determine when writes are able to occur to * a filesystem. */ /* * __mnt_is_readonly: check whether a mount is read-only * @mnt: the mount to check for its write status * * This shouldn't be used directly ouside of the VFS. * It does not guarantee that the filesystem will stay * r/w, just that it is right *now*. This can not and * should not be used in place of IS_RDONLY(inode). * mnt_want/drop_write() will _keep_ the filesystem * r/w. */ int __mnt_is_readonly(struct vfsmount *mnt) { if (mnt->mnt_flags & MNT_READONLY) return 1; if (mnt->mnt_sb->s_flags & MS_RDONLY) return 1; return 0; } EXPORT_SYMBOL_GPL(__mnt_is_readonly); static inline void inc_mnt_writers(struct vfsmount *mnt) { #ifdef CONFIG_SMP (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))++; #else mnt->mnt_writers++; #endif } static inline void dec_mnt_writers(struct vfsmount *mnt) { #ifdef CONFIG_SMP (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))--; #else mnt->mnt_writers--; #endif } static unsigned int count_mnt_writers(struct vfsmount *mnt) { #ifdef CONFIG_SMP unsigned int count = 0; int cpu; for_each_possible_cpu(cpu) { count += *per_cpu_ptr(mnt->mnt_writers, cpu); } return count; #else return mnt->mnt_writers; #endif } /* * Most r/o checks on a fs are for operations that take * discrete amounts of time, like a write() or unlink(). * We must keep track of when those operations start * (for permission checks) and when they end, so that * we can determine when writes are able to occur to * a filesystem. */ /** * mnt_want_write - get write access to a mount * @mnt: the mount on which to take a write * * This tells the low-level filesystem that a write is * about to be performed to it, and makes sure that * writes are allowed before returning success. When * the write operation is finished, mnt_drop_write() * must be called. This is effectively a refcount. */ int mnt_want_write(struct vfsmount *mnt) { int ret = 0; preempt_disable(); inc_mnt_writers(mnt); /* * The store to inc_mnt_writers must be visible before we pass * MNT_WRITE_HOLD loop below, so that the slowpath can see our * incremented count after it has set MNT_WRITE_HOLD. */ smp_mb(); while (mnt->mnt_flags & MNT_WRITE_HOLD) cpu_relax(); /* * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will * be set to match its requirements. So we must not load that until * MNT_WRITE_HOLD is cleared. */ smp_rmb(); if (__mnt_is_readonly(mnt)) { dec_mnt_writers(mnt); ret = -EROFS; goto out; } out: preempt_enable(); return ret; } EXPORT_SYMBOL_GPL(mnt_want_write); /** * mnt_clone_write - get write access to a mount * @mnt: the mount on which to take a write * * This is effectively like mnt_want_write, except * it must only be used to take an extra write reference * on a mountpoint that we already know has a write reference * on it. This allows some optimisation. * * After finished, mnt_drop_write must be called as usual to * drop the reference. */ int mnt_clone_write(struct vfsmount *mnt) { /* superblock may be r/o */ if (__mnt_is_readonly(mnt)) return -EROFS; preempt_disable(); inc_mnt_writers(mnt); preempt_enable(); return 0; } EXPORT_SYMBOL_GPL(mnt_clone_write); /** * mnt_want_write_file - get write access to a file's mount * @file: the file who's mount on which to take a write * * This is like mnt_want_write, but it takes a file and can * do some optimisations if the file is open for write already */ int mnt_want_write_file(struct file *file) { struct inode *inode = file->f_dentry->d_inode; if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) return mnt_want_write(file->f_path.mnt); else return mnt_clone_write(file->f_path.mnt); } EXPORT_SYMBOL_GPL(mnt_want_write_file); /** * mnt_drop_write - give up write access to a mount * @mnt: the mount on which to give up write access * * Tells the low-level filesystem that we are done * performing writes to it. Must be matched with * mnt_want_write() call above. */ void mnt_drop_write(struct vfsmount *mnt) { preempt_disable(); dec_mnt_writers(mnt); preempt_enable(); } EXPORT_SYMBOL_GPL(mnt_drop_write); static int mnt_make_readonly(struct vfsmount *mnt) { int ret = 0; spin_lock(&vfsmount_lock); mnt->mnt_flags |= MNT_WRITE_HOLD; /* * After storing MNT_WRITE_HOLD, we'll read the counters. This store * should be visible before we do. */ smp_mb(); /* * 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 (count_mnt_writers(mnt) > 0) ret = -EBUSY; else 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_flags &= ~MNT_WRITE_HOLD; spin_unlock(&vfsmount_lock); return ret; } static void __mnt_unmake_readonly(struct vfsmount *mnt) { spin_lock(&vfsmount_lock); mnt->mnt_flags &= ~MNT_READONLY; spin_unlock(&vfsmount_lock); } void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) { mnt->mnt_sb = sb; mnt->mnt_root = dget(sb->s_root); } EXPORT_SYMBOL(simple_set_mnt); void free_vfsmnt(struct vfsmount *mnt) { kfree(mnt->mnt_devname); mnt_free_id(mnt); #ifdef CONFIG_SMP free_percpu(mnt->mnt_writers); #endif kmem_cache_free(mnt_cache, mnt); } /* * find the first or last mount at @dentry on vfsmount @mnt depending on * @dir. If @dir is set return the first mount else return the last mount. */ struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, int dir) { struct list_head *head = mount_hashtable + hash(mnt, dentry); struct list_head *tmp = head; struct vfsmount *p, *found = NULL; for (;;) { tmp = dir ? tmp->next : tmp->prev; p = NULL; if (tmp == head) break; p = list_entry(tmp, struct vfsmount, mnt_hash); if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { found = p; break; } } return found; } /* * lookup_mnt increments the ref count before returning * the vfsmount struct. */ struct vfsmount *lookup_mnt(struct path *path) { struct vfsmount *child_mnt; spin_lock(&vfsmount_lock); if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) mntget(child_mnt); spin_unlock(&vfsmount_lock); return child_mnt; } static inline int check_mnt(struct vfsmount *mnt) { return mnt->mnt_ns == current->nsproxy->mnt_ns; } static void touch_mnt_namespace(struct mnt_namespace *ns) { if (ns) { ns->event = ++event; wake_up_interruptible(&ns->poll); } } static void __touch_mnt_namespace(struct mnt_namespace *ns) { if (ns && ns->event != event) { ns->event = event; wake_up_interruptible(&ns->poll); } } static void detach_mnt(struct vfsmount *mnt, struct path *old_path) { old_path->dentry = mnt->mnt_mountpoint; old_path->mnt = mnt->mnt_parent; mnt->mnt_parent = mnt; mnt->mnt_mountpoint = mnt->mnt_root; list_del_init(&mnt->mnt_child); list_del_init(&mnt->mnt_hash); old_path->dentry->d_mounted--; } void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, struct vfsmount *child_mnt) { child_mnt->mnt_parent = mntget(mnt); child_mnt->mnt_mountpoint = dget(dentry); dentry->d_mounted++; } static void attach_mnt(struct vfsmount *mnt, struct path *path) { mnt_set_mountpoint(path->mnt, path->dentry, mnt); list_add_tail(&mnt->mnt_hash, mount_hashtable + hash(path->mnt, path->dentry)); list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts); } /* * the caller must hold vfsmount_lock */ static void commit_tree(struct vfsmount *mnt) { struct vfsmount *parent = mnt->mnt_parent; struct vfsmount *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); list_add_tail(&mnt->mnt_hash, mount_hashtable + hash(parent, mnt->mnt_mountpoint)); list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); touch_mnt_namespace(n); } static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *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 vfsmount, mnt_child); } static struct vfsmount *skip_mnt_tree(struct vfsmount *p) { struct list_head *prev = p->mnt_mounts.prev; while (prev != &p->mnt_mounts) { p = list_entry(prev, struct vfsmount, mnt_child); prev = p->mnt_mounts.prev; } return p; } static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, int flag) { struct super_block *sb = old->mnt_sb; struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); if (mnt) { if (flag & (CL_SLAVE | CL_PRIVATE)) 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) { int err = mnt_alloc_group_id(mnt); if (err) goto out_free; } mnt->mnt_flags = old->mnt_flags; atomic_inc(&sb->s_active); mnt->mnt_sb = sb; mnt->mnt_root = dget(root); mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; if (flag & CL_SLAVE) { 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: free_vfsmnt(mnt); return NULL; } static inline void __mntput(struct vfsmount *mnt) { struct super_block *sb = mnt->mnt_sb; /* * 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. */ /* * atomic_dec_and_lock() used to deal with ->mnt_count decrements * provides barriers, so count_mnt_writers() below is safe. AV */ WARN_ON(count_mnt_writers(mnt)); dput(mnt->mnt_root); free_vfsmnt(mnt); deactivate_super(sb); } void mntput_no_expire(struct vfsmount *mnt) { repeat: if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { if (likely(!mnt->mnt_pinned)) { spin_unlock(&vfsmount_lock); __mntput(mnt); return; } atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); mnt->mnt_pinned = 0; spin_unlock(&vfsmount_lock); acct_auto_close_mnt(mnt); goto repeat; } } EXPORT_SYMBOL(mntput_no_expire); void mnt_pin(struct vfsmount *mnt) { spin_lock(&vfsmount_lock); mnt->mnt_pinned++; spin_unlock(&vfsmount_lock); } EXPORT_SYMBOL(mnt_pin); void mnt_unpin(struct vfsmount *mnt) { spin_lock(&vfsmount_lock); if (mnt->mnt_pinned) { atomic_inc(&mnt->mnt_count); mnt->mnt_pinned--; } spin_unlock(&vfsmount_lock); } EXPORT_SYMBOL(mnt_unpin); 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 vfsmount *mnt) { const char *options; rcu_read_lock(); options = rcu_dereference(mnt->mnt_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 */ static void *m_start(struct seq_file *m, loff_t *pos) { struct proc_mounts *p = m->private; down_read(&namespace_sem); return seq_list_start(&p->ns->list, *pos); } static void *m_next(struct seq_file *m, void *v, loff_t *pos) { struct proc_mounts *p = m->private; return seq_list_next(v, &p->ns->list, pos); } static void m_stop(struct seq_file *m, void *v) { up_read(&namespace_sem); } int mnt_had_events(struct proc_mounts *p) { struct mnt_namespace *ns = p->ns; int res = 0; spin_lock(&vfsmount_lock); if (p->event != ns->event) { p->event = ns->event; res = 1; } spin_unlock(&vfsmount_lock); return res; } struct proc_fs_info { int flag; const char *str; }; static int show_sb_opts(struct seq_file *m, struct super_block *sb) { static const struct proc_fs_info fs_info[] = { { MS_SYNCHRONOUS, ",sync" }, { MS_DIRSYNC, ",dirsync" }, { MS_MANDLOCK, ",mand" }, { 0, NULL } }; const struct proc_fs_info *fs_infop; for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { if (sb->s_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } return security_sb_show_options(m, sb); } static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) { static const struct proc_fs_info mnt_info[] = { { MNT_NOSUID, ",nosuid" }, { MNT_NODEV, ",nodev" }, { MNT_NOEXEC, ",noexec" }, { MNT_NOATIME, ",noatime" }, { MNT_NODIRATIME, ",nodiratime" }, { MNT_RELATIME, ",relatime" }, { MNT_STRICTATIME, ",strictatime" }, { 0, NULL } }; const struct proc_fs_info *fs_infop; for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { if (mnt->mnt_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } } static void show_type(struct seq_file *m, struct super_block *sb) { mangle(m, sb->s_type->name); if (sb->s_subtype && sb->s_subtype[0]) { seq_putc(m, '.'); mangle(m, sb->s_subtype); } } static int show_vfsmnt(struct seq_file *m, void *v) { struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); int err = 0; struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); seq_putc(m, ' '); seq_path(m, &mnt_path, " \t\n\\"); seq_putc(m, ' '); show_type(m, mnt->mnt_sb); seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw"); err = show_sb_opts(m, mnt->mnt_sb); if (err) goto out; show_mnt_opts(m, mnt); if (mnt->mnt_sb->s_op->show_options) err = mnt->mnt_sb->s_op->show_options(m, mnt); seq_puts(m, " 0 0\n"); out: return err; } const struct seq_operations mounts_op = { .start = m_start, .next = m_next, .stop = m_stop, .show = show_vfsmnt }; static int show_mountinfo(struct seq_file *m, void *v) { struct proc_mounts *p = m->private; struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); struct super_block *sb = mnt->mnt_sb; struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; struct path root = p->root; int err = 0; seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id, MAJOR(sb->s_dev), MINOR(sb->s_dev)); seq_dentry(m, mnt->mnt_root, " \t\n\\"); seq_putc(m, ' '); seq_path_root(m, &mnt_path, &root, " \t\n\\"); if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) { /* * Mountpoint is outside root, discard that one. Ugly, * but less so than trying to do that in iterator in a * race-free way (due to renames). */ return SEQ_SKIP; } seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); show_mnt_opts(m, mnt); /* Tagged fields ("foo:X" or "bar") */ if (IS_MNT_SHARED(mnt)) seq_printf(m, " shared:%i", mnt->mnt_group_id); if (IS_MNT_SLAVE(mnt)) { int master = mnt->mnt_master->mnt_group_id; int dom = get_dominating_id(mnt, &p->root); seq_printf(m, " master:%i", master); if (dom && dom != master) seq_printf(m, " propagate_from:%i", dom); } if (IS_MNT_UNBINDABLE(mnt)) seq_puts(m, " unbindable"); /* Filesystem specific data */ seq_puts(m, " - "); show_type(m, sb); seq_putc(m, ' '); mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); err = show_sb_opts(m, sb); if (err) goto out; if (sb->s_op->show_options) err = sb->s_op->show_options(m, mnt); seq_putc(m, '\n'); out: return err; } const struct seq_operations mountinfo_op = { .start = m_start, .next = m_next, .stop = m_stop, .show = show_mountinfo, }; static int show_vfsstat(struct seq_file *m, void *v) { struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; int err = 0; /* device */ if (mnt->mnt_devname) { seq_puts(m, "device "); mangle(m, mnt->mnt_devname); } else seq_puts(m, "no device"); /* mount point */ seq_puts(m, " mounted on "); seq_path(m, &mnt_path, " \t\n\\"); seq_putc(m, ' '); /* file system type */ seq_puts(m, "with fstype "); show_type(m, mnt->mnt_sb); /* optional statistics */ if (mnt->mnt_sb->s_op->show_stats) { seq_putc(m, ' '); err = mnt->mnt_sb->s_op->show_stats(m, mnt); } seq_putc(m, '\n'); return err; } const struct seq_operations mountstats_op = { .start = m_start, .next = m_next, .stop = m_stop, .show = show_vfsstat, }; #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 *mnt) { int actual_refs = 0; int minimum_refs = 0; struct vfsmount *p; spin_lock(&vfsmount_lock); for (p = mnt; p; p = next_mnt(p, mnt)) { actual_refs += atomic_read(&p->mnt_count); minimum_refs += 2; } spin_unlock(&vfsmount_lock); 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); spin_lock(&vfsmount_lock); if (propagate_mount_busy(mnt, 2)) ret = 0; spin_unlock(&vfsmount_lock); up_read(&namespace_sem); return ret; } EXPORT_SYMBOL(may_umount); void release_mounts(struct list_head *head) { struct vfsmount *mnt; while (!list_empty(head)) { mnt = list_first_entry(head, struct vfsmount, mnt_hash); list_del_init(&mnt->mnt_hash); if (mnt->mnt_parent != mnt) { struct dentry *dentry; struct vfsmount *m; spin_lock(&vfsmount_lock); dentry = mnt->mnt_mountpoint; m = mnt->mnt_parent; mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; m->mnt_ghosts--; spin_unlock(&vfsmount_lock); dput(dentry); mntput(m); } mntput(mnt); } } void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) { struct vfsmount *p; for (p = mnt; p; p = next_mnt(p, mnt)) list_move(&p->mnt_hash, kill); if (propagate) propagate_umount(kill); list_for_each_entry(p, kill, mnt_hash) { list_del_init(&p->mnt_expire); list_del_init(&p->mnt_list); __touch_mnt_namespace(p->mnt_ns); p->mnt_ns = NULL; list_del_init(&p->mnt_child); if (p->mnt_parent != p) { p->mnt_parent->mnt_ghosts++; p->mnt_mountpoint->d_mounted--; } change_mnt_propagation(p, MS_PRIVATE); } } static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts); static int do_umount(struct vfsmount *mnt, int flags) { struct super_block *sb = mnt->mnt_sb; int retval; LIST_HEAD(umount_list); retval = security_sb_umount(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 == current->fs->root.mnt || flags & (MNT_FORCE | MNT_DETACH)) return -EINVAL; if (atomic_read(&mnt->mnt_count) != 2) return -EBUSY; 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 == current->fs->root.mnt && !(flags & MNT_DETACH)) { /* * Special case for "unmounting" root ... * we just try to remount it readonly. */ 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; } down_write(&namespace_sem); spin_lock(&vfsmount_lock); event++; if (!(flags & MNT_DETACH)) shrink_submounts(mnt, &umount_list); retval = -EBUSY; if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { if (!list_empty(&mnt->mnt_list)) umount_tree(mnt, 1, &umount_list); retval = 0; } spin_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); return retval; } /* * 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; int retval; int lookup_flags = 0; if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) return -EINVAL; if (!(flags & UMOUNT_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); if (retval) goto out; retval = -EINVAL; if (path.dentry != path.mnt->mnt_root) goto dput_and_out; if (!check_mnt(path.mnt)) goto dput_and_out; retval = -EPERM; if (!capable(CAP_SYS_ADMIN)) goto dput_and_out; retval = do_umount(path.mnt, flags); dput_and_out: /* we mustn't call path_put() as that would clear mnt_expiry_mark */ dput(path.dentry); mntput_no_expire(path.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 int mount_is_safe(struct path *path) { if (capable(CAP_SYS_ADMIN)) return 0; return -EPERM; #ifdef notyet if (S_ISLNK(path->dentry->d_inode->i_mode)) return -EPERM; if (path->dentry->d_inode->i_mode & S_ISVTX) { if (current_uid() != path->dentry->d_inode->i_uid) return -EPERM; } if (inode_permission(path->dentry->d_inode, MAY_WRITE)) return -EPERM; return 0; #endif } struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, int flag) { struct vfsmount *res, *p, *q, *r, *s; struct path path; if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) return NULL; res = q = clone_mnt(mnt, dentry, flag); if (!q) goto Enomem; q->mnt_mountpoint = mnt->mnt_mountpoint; p = mnt; list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { if (!is_subdir(r->mnt_mountpoint, dentry)) continue; for (s = r; s; s = next_mnt(s, r)) { if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { s = skip_mnt_tree(s); continue; } while (p != s->mnt_parent) { p = p->mnt_parent; q = q->mnt_parent; } p = s; path.mnt = q; path.dentry = p->mnt_mountpoint; q = clone_mnt(p, p->mnt_root, flag); if (!q) goto Enomem; spin_lock(&vfsmount_lock); list_add_tail(&q->mnt_list, &res->mnt_list); attach_mnt(q, &path); spin_unlock(&vfsmount_lock); } } return res; Enomem: if (res) { LIST_HEAD(umount_list); spin_lock(&vfsmount_lock); umount_tree(res, 0, &umount_list); spin_unlock(&vfsmount_lock); release_mounts(&umount_list); } return NULL; } struct vfsmount *collect_mounts(struct path *path) { struct vfsmount *tree; down_write(&namespace_sem); tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE); up_write(&namespace_sem); return tree; } void drop_collected_mounts(struct vfsmount *mnt) { LIST_HEAD(umount_list); down_write(&namespace_sem); spin_lock(&vfsmount_lock); umount_tree(mnt, 0, &umount_list); spin_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); } int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, struct vfsmount *root) { struct vfsmount *mnt; int res = f(root, arg); if (res) return res; list_for_each_entry(mnt, &root->mnt_list, mnt_list) { res = f(mnt, arg); if (res) return res; } return 0; } static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end) { struct vfsmount *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 vfsmount *mnt, bool recurse) { struct vfsmount *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 vfsmount *source_mnt, struct path *path, struct path *parent_path) { LIST_HEAD(tree_list); struct vfsmount *dest_mnt = path->mnt; struct dentry *dest_dentry = path->dentry; struct vfsmount *child, *p; 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_dentry, source_mnt, &tree_list); if (err) goto out_cleanup_ids; spin_lock(&vfsmount_lock); if (IS_MNT_SHARED(dest_mnt)) { for (p = source_mnt; p; p = next_mnt(p, source_mnt)) set_mnt_shared(p); } if (parent_path) { detach_mnt(source_mnt, parent_path); attach_mnt(source_mnt, path); touch_mnt_namespace(parent_path->mnt->mnt_ns); } else { mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); commit_tree(source_mnt); } list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { list_del_init(&child->mnt_hash); commit_tree(child); } spin_unlock(&vfsmount_lock); return 0; out_cleanup_ids: if (IS_MNT_SHARED(dest_mnt)) cleanup_group_ids(source_mnt, NULL); out: return err; } static int graft_tree(struct vfsmount *mnt, struct path *path) { int err; if (mnt->mnt_sb->s_flags & MS_NOUSER) return -EINVAL; if (S_ISDIR(path->dentry->d_inode->i_mode) != S_ISDIR(mnt->mnt_root->d_inode->i_mode)) return -ENOTDIR; err = -ENOENT; mutex_lock(&path->dentry->d_inode->i_mutex); if (cant_mount(path->dentry)) goto out_unlock; if (!d_unlinked(path->dentry)) err = attach_recursive_mnt(mnt, path, NULL); out_unlock: mutex_unlock(&path->dentry->d_inode->i_mutex); return err; } /* * recursively change the type of the mountpoint. */ static int do_change_type(struct path *path, int flag) { struct vfsmount *m, *mnt = path->mnt; int recurse = flag & MS_REC; int type = flag & ~MS_REC; int err = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (path->dentry != path->mnt->mnt_root) return -EINVAL; down_write(&namespace_sem); if (type == MS_SHARED) { err = invent_group_ids(mnt, recurse); if (err) goto out_unlock; } spin_lock(&vfsmount_lock); for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) change_mnt_propagation(m, type); spin_unlock(&vfsmount_lock); out_unlock: up_write(&namespace_sem); return err; } /* * do loopback mount. */ static int do_loopback(struct path *path, char *old_name, int recurse) { struct path old_path; struct vfsmount *mnt = NULL; int err = mount_is_safe(path); if (err) return err; if (!old_name || !*old_name) return -EINVAL; err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); if (err) return err; down_write(&namespace_sem); err = -EINVAL; if (IS_MNT_UNBINDABLE(old_path.mnt)) goto out; if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) goto out; err = -ENOMEM; if (recurse) mnt = copy_tree(old_path.mnt, old_path.dentry, 0); else mnt = clone_mnt(old_path.mnt, old_path.dentry, 0); if (!mnt) goto out; err = graft_tree(mnt, path); if (err) { LIST_HEAD(umount_list); spin_lock(&vfsmount_lock); umount_tree(mnt, 0, &umount_list); spin_unlock(&vfsmount_lock); release_mounts(&umount_list); } out: up_write(&namespace_sem); 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(mnt); else __mnt_unmake_readonly(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; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!check_mnt(path->mnt)) return -EINVAL; if (path->dentry != path->mnt->mnt_root) return -EINVAL; down_write(&sb->s_umount); if (flags & MS_BIND) err = change_mount_flags(path->mnt, flags); else err = do_remount_sb(sb, flags, data, 0); if (!err) { spin_lock(&vfsmount_lock); mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK; path->mnt->mnt_flags = mnt_flags; spin_unlock(&vfsmount_lock); } up_write(&sb->s_umount); if (!err) { spin_lock(&vfsmount_lock); touch_mnt_namespace(path->mnt->mnt_ns); spin_unlock(&vfsmount_lock); } return err; } static inline int tree_contains_unbindable(struct vfsmount *mnt) { struct vfsmount *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, char *old_name) { struct path old_path, parent_path; struct vfsmount *p; int err = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!old_name || !*old_name) return -EINVAL; err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); if (err) return err; down_write(&namespace_sem); while (d_mountpoint(path->dentry) && follow_down(path)) ; err = -EINVAL; if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) goto out; err = -ENOENT; mutex_lock(&path->dentry->d_inode->i_mutex); if (cant_mount(path->dentry)) goto out1; if (d_unlinked(path->dentry)) goto out1; err = -EINVAL; if (old_path.dentry != old_path.mnt->mnt_root) goto out1; if (old_path.mnt == old_path.mnt->mnt_parent) 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 (old_path.mnt->mnt_parent && IS_MNT_SHARED(old_path.mnt->mnt_parent)) goto out1; /* * Don't move a mount tree containing unbindable mounts to a destination * mount which is shared. */ if (IS_MNT_SHARED(path->mnt) && tree_contains_unbindable(old_path.mnt)) goto out1; err = -ELOOP; for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent) if (p == old_path.mnt) goto out1; err = attach_recursive_mnt(old_path.mnt, path, &parent_path); if (err) goto out1; /* if the mount is moved, it should no longer be expire * automatically */ list_del_init(&old_path.mnt->mnt_expire); out1: mutex_unlock(&path->dentry->d_inode->i_mutex); out: up_write(&namespace_sem); if (!err) path_put(&parent_path); path_put(&old_path); 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, char *type, int flags, int mnt_flags, char *name, void *data) { struct vfsmount *mnt; if (!type) return -EINVAL; /* we need capabilities... */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; lock_kernel(); mnt = do_kern_mount(type, flags, name, data); unlock_kernel(); if (IS_ERR(mnt)) return PTR_ERR(mnt); return do_add_mount(mnt, path, mnt_flags, NULL); } /* * add a mount into a namespace's mount tree * - provide the option of adding the new mount to an expiration list */ int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags, struct list_head *fslist) { int err; mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); down_write(&namespace_sem); /* Something was mounted here while we slept */ while (d_mountpoint(path->dentry) && follow_down(path)) ; err = -EINVAL; if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt)) goto unlock; /* Refuse the same filesystem on the same mount point */ err = -EBUSY; if (path->mnt->mnt_sb == newmnt->mnt_sb && path->mnt->mnt_root == path->dentry) goto unlock; err = -EINVAL; if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) goto unlock; newmnt->mnt_flags = mnt_flags; if ((err = graft_tree(newmnt, path))) goto unlock; if (fslist) /* add to the specified expiration list */ list_add_tail(&newmnt->mnt_expire, fslist); up_write(&namespace_sem); return 0; unlock: up_write(&namespace_sem); mntput(newmnt); return err; } EXPORT_SYMBOL_GPL(do_add_mount); /* * 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 vfsmount *mnt, *next; LIST_HEAD(graveyard); LIST_HEAD(umounts); if (list_empty(mounts)) return; down_write(&namespace_sem); spin_lock(&vfsmount_lock); /* 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 vfsmount, mnt_expire); touch_mnt_namespace(mnt->mnt_ns); umount_tree(mnt, 1, &umounts); } spin_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umounts); } 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 vfsmount *parent, struct list_head *graveyard) { struct vfsmount *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 vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); next = tmp->next; if (!(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 */ static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts) { LIST_HEAD(graveyard); struct vfsmount *m; /* extract submounts of 'mountpoint' from the expiration list */ while (select_submounts(mnt, &graveyard)) { while (!list_empty(&graveyard)) { m = list_first_entry(&graveyard, struct vfsmount, mnt_expire); touch_mnt_namespace(m->mnt_ns); umount_tree(m, 1, umounts); } } } /* * 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; } int copy_mount_string(const void __user *data, char **where) { char *tmp; if (!data) { *where = NULL; return 0; } tmp = strndup_user(data, PAGE_SIZE); if (IS_ERR(tmp)) return PTR_ERR(tmp); *where = tmp; return 0; } /* * 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(char *dev_name, char *dir_name, 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 (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) return -EINVAL; if (data_page) ((char *)data_page)[PAGE_SIZE - 1] = 0; /* ... and get the mountpoint */ retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); if (retval) return retval; retval = security_sb_mount(dev_name, &path, type_page, flags, data_page); 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; flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | 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 struct mnt_namespace *alloc_mnt_ns(void) { struct mnt_namespace *new_ns; new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); if (!new_ns) return ERR_PTR(-ENOMEM); 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; return new_ns; } /* * Allocate a new namespace structure and populate it with contents * copied from the namespace of the passed in task structure. */ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, struct fs_struct *fs) { struct mnt_namespace *new_ns; struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; struct vfsmount *p, *q; new_ns = alloc_mnt_ns(); if (IS_ERR(new_ns)) return new_ns; down_write(&namespace_sem); /* First pass: copy the tree topology */ new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, CL_COPY_ALL | CL_EXPIRE); if (!new_ns->root) { up_write(&namespace_sem); kfree(new_ns); return ERR_PTR(-ENOMEM); } spin_lock(&vfsmount_lock); list_add_tail(&new_ns->list, &new_ns->root->mnt_list); spin_unlock(&vfsmount_lock); /* * 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 = mnt_ns->root; q = new_ns->root; while (p) { q->mnt_ns = new_ns; if (fs) { if (p == fs->root.mnt) { rootmnt = p; fs->root.mnt = mntget(q); } if (p == fs->pwd.mnt) { pwdmnt = p; fs->pwd.mnt = mntget(q); } } p = next_mnt(p, mnt_ns->root); q = next_mnt(q, new_ns->root); } up_write(&namespace_sem); if (rootmnt) mntput(rootmnt); if (pwdmnt) mntput(pwdmnt); return new_ns; } struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, struct fs_struct *new_fs) { struct mnt_namespace *new_ns; BUG_ON(!ns); get_mnt_ns(ns); if (!(flags & CLONE_NEWNS)) return ns; new_ns = dup_mnt_ns(ns, new_fs); put_mnt_ns(ns); return new_ns; } /** * create_mnt_ns - creates a private namespace and adds a root filesystem * @mnt: pointer to the new root filesystem mountpoint */ struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) { struct mnt_namespace *new_ns; new_ns = alloc_mnt_ns(); if (!IS_ERR(new_ns)) { mnt->mnt_ns = new_ns; new_ns->root = mnt; list_add(&new_ns->list, &new_ns->root->mnt_list); } return new_ns; } EXPORT_SYMBOL(create_mnt_ns); 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_dir; char *kernel_dev; unsigned long data_page; ret = copy_mount_string(type, &kernel_type); if (ret < 0) goto out_type; kernel_dir = getname(dir_name); if (IS_ERR(kernel_dir)) { ret = PTR_ERR(kernel_dir); goto out_dir; } ret = copy_mount_string(dev_name, &kernel_dev); if (ret < 0) goto out_dev; ret = copy_mount_options(data, &data_page); if (ret < 0) goto out_data; ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, (void *) data_page); free_page(data_page); out_data: kfree(kernel_dev); out_dev: putname(kernel_dir); out_dir: kfree(kernel_type); out_type: return ret; } /* * 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 vfsmount *tmp; struct path new, old, parent_path, root_parent, root; int error; if (!capable(CAP_SYS_ADMIN)) return -EPERM; error = user_path_dir(new_root, &new); if (error) goto out0; error = -EINVAL; if (!check_mnt(new.mnt)) goto out1; error = user_path_dir(put_old, &old); if (error) goto out1; error = security_sb_pivotroot(&old, &new); if (error) { path_put(&old); goto out1; } read_lock(¤t->fs->lock); root = current->fs->root; path_get(¤t->fs->root); read_unlock(¤t->fs->lock); down_write(&namespace_sem); mutex_lock(&old.dentry->d_inode->i_mutex); error = -EINVAL; if (IS_MNT_SHARED(old.mnt) || IS_MNT_SHARED(new.mnt->mnt_parent) || IS_MNT_SHARED(root.mnt->mnt_parent)) goto out2; if (!check_mnt(root.mnt)) goto out2; error = -ENOENT; if (cant_mount(old.dentry)) goto out2; if (d_unlinked(new.dentry)) goto out2; if (d_unlinked(old.dentry)) goto out2; error = -EBUSY; if (new.mnt == root.mnt || old.mnt == root.mnt) goto out2; /* loop, on the same file system */ error = -EINVAL; if (root.mnt->mnt_root != root.dentry) goto out2; /* not a mountpoint */ if (root.mnt->mnt_parent == root.mnt) goto out2; /* not attached */ if (new.mnt->mnt_root != new.dentry) goto out2; /* not a mountpoint */ if (new.mnt->mnt_parent == new.mnt) goto out2; /* not attached */ /* make sure we can reach put_old from new_root */ tmp = old.mnt; spin_lock(&vfsmount_lock); if (tmp != new.mnt) { for (;;) { if (tmp->mnt_parent == tmp) goto out3; /* already mounted on put_old */ if (tmp->mnt_parent == new.mnt) break; tmp = tmp->mnt_parent; } if (!is_subdir(tmp->mnt_mountpoint, new.dentry)) goto out3; } else if (!is_subdir(old.dentry, new.dentry)) goto out3; detach_mnt(new.mnt, &parent_path); detach_mnt(root.mnt, &root_parent); /* mount old root on put_old */ attach_mnt(root.mnt, &old); /* mount new_root on / */ attach_mnt(new.mnt, &root_parent); touch_mnt_namespace(current->nsproxy->mnt_ns); spin_unlock(&vfsmount_lock); chroot_fs_refs(&root, &new); error = 0; path_put(&root_parent); path_put(&parent_path); out2: mutex_unlock(&old.dentry->d_inode->i_mutex); up_write(&namespace_sem); path_put(&root); path_put(&old); out1: path_put(&new); out0: return error; out3: spin_unlock(&vfsmount_lock); goto out2; } static void __init init_mount_tree(void) { struct vfsmount *mnt; struct mnt_namespace *ns; struct path root; mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); 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 = ns->root; root.dentry = ns->root->mnt_root; set_fs_pwd(current->fs, &root); set_fs_root(current->fs, &root); } void __init mnt_init(void) { unsigned u; int err; init_rwsem(&namespace_sem); mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); if (!mount_hashtable) panic("Failed to allocate mount hash table\n"); printk("Mount-cache hash table entries: %lu\n", HASH_SIZE); for (u = 0; u < HASH_SIZE; u++) INIT_LIST_HEAD(&mount_hashtable[u]); 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) { LIST_HEAD(umount_list); if (!atomic_dec_and_test(&ns->count)) return; down_write(&namespace_sem); spin_lock(&vfsmount_lock); umount_tree(ns->root, 0, &umount_list); spin_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); kfree(ns); } EXPORT_SYMBOL(put_mnt_ns);