linux/fs/proc/inode.c

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/*
* linux/fs/proc/inode.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/kernel.h>
#include <linux/pid_namespace.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
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#include <linux/completion.h>
#include <linux/poll.h>
#include <linux/printk.h>
#include <linux/file.h>
#include <linux/limits.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/seq_file.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
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#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/magic.h>
#include <asm/uaccess.h>
#include "internal.h"
static void proc_evict_inode(struct inode *inode)
{
struct proc_dir_entry *de;
struct ctl_table_header *head;
mm + fs: store shadow entries in page cache Reclaim will be leaving shadow entries in the page cache radix tree upon evicting the real page. As those pages are found from the LRU, an iput() can lead to the inode being freed concurrently. At this point, reclaim must no longer install shadow pages because the inode freeing code needs to ensure the page tree is really empty. Add an address_space flag, AS_EXITING, that the inode freeing code sets under the tree lock before doing the final truncate. Reclaim will check for this flag before installing shadow pages. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Greg Thelen <gthelen@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jan Kara <jack@suse.cz> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Luigi Semenzato <semenzato@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Metin Doslu <metin@citusdata.com> Cc: Michel Lespinasse <walken@google.com> Cc: Ozgun Erdogan <ozgun@citusdata.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Roman Gushchin <klamm@yandex-team.ru> Cc: Ryan Mallon <rmallon@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
/* Stop tracking associated processes */
put_pid(PROC_I(inode)->pid);
/* Let go of any associated proc directory entry */
de = PDE(inode);
if (de)
pde_put(de);
head = PROC_I(inode)->sysctl;
if (head) {
RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
sysctl_head_put(head);
}
}
static struct kmem_cache * proc_inode_cachep;
static struct inode *proc_alloc_inode(struct super_block *sb)
{
struct proc_inode *ei;
struct inode *inode;
ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
if (!ei)
return NULL;
ei->pid = NULL;
ei->fd = 0;
ei->op.proc_get_link = NULL;
ei->pde = NULL;
ei->sysctl = NULL;
ei->sysctl_entry = NULL;
ei->ns_ops = NULL;
inode = &ei->vfs_inode;
return inode;
}
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static void proc_i_callback(struct rcu_head *head)
{
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struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(proc_inode_cachep, PROC_I(inode));
}
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static void proc_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, proc_i_callback);
}
static void init_once(void *foo)
{
struct proc_inode *ei = (struct proc_inode *) foo;
inode_init_once(&ei->vfs_inode);
}
void __init proc_init_inodecache(void)
{
proc_inode_cachep = kmem_cache_create("proc_inode_cache",
sizeof(struct proc_inode),
0, (SLAB_RECLAIM_ACCOUNT|
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SLAB_MEM_SPREAD|SLAB_ACCOUNT|
SLAB_PANIC),
init_once);
}
static int proc_show_options(struct seq_file *seq, struct dentry *root)
{
procfs: add hidepid= and gid= mount options Add support for mount options to restrict access to /proc/PID/ directories. The default backward-compatible "relaxed" behaviour is left untouched. The first mount option is called "hidepid" and its value defines how much info about processes we want to be available for non-owners: hidepid=0 (default) means the old behavior - anybody may read all world-readable /proc/PID/* files. hidepid=1 means users may not access any /proc/<pid>/ directories, but their own. Sensitive files like cmdline, sched*, status are now protected against other users. As permission checking done in proc_pid_permission() and files' permissions are left untouched, programs expecting specific files' modes are not confused. hidepid=2 means hidepid=1 plus all /proc/PID/ will be invisible to other users. It doesn't mean that it hides whether a process exists (it can be learned by other means, e.g. by kill -0 $PID), but it hides process' euid and egid. It compicates intruder's task of gathering info about running processes, whether some daemon runs with elevated privileges, whether another user runs some sensitive program, whether other users run any program at all, etc. gid=XXX defines a group that will be able to gather all processes' info (as in hidepid=0 mode). This group should be used instead of putting nonroot user in sudoers file or something. However, untrusted users (like daemons, etc.) which are not supposed to monitor the tasks in the whole system should not be added to the group. hidepid=1 or higher is designed to restrict access to procfs files, which might reveal some sensitive private information like precise keystrokes timings: http://www.openwall.com/lists/oss-security/2011/11/05/3 hidepid=1/2 doesn't break monitoring userspace tools. ps, top, pgrep, and conky gracefully handle EPERM/ENOENT and behave as if the current user is the only user running processes. pstree shows the process subtree which contains "pstree" process. Note: the patch doesn't deal with setuid/setgid issues of keeping preopened descriptors of procfs files (like https://lkml.org/lkml/2011/2/7/368). We rely on that the leaked information like the scheduling counters of setuid apps doesn't threaten anybody's privacy - only the user started the setuid program may read the counters. Signed-off-by: Vasiliy Kulikov <segoon@openwall.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Greg KH <greg@kroah.com> Cc: Theodore Tso <tytso@MIT.EDU> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: James Morris <jmorris@namei.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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struct super_block *sb = root->d_sb;
struct pid_namespace *pid = sb->s_fs_info;
if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
procfs: add hidepid= and gid= mount options Add support for mount options to restrict access to /proc/PID/ directories. The default backward-compatible "relaxed" behaviour is left untouched. The first mount option is called "hidepid" and its value defines how much info about processes we want to be available for non-owners: hidepid=0 (default) means the old behavior - anybody may read all world-readable /proc/PID/* files. hidepid=1 means users may not access any /proc/<pid>/ directories, but their own. Sensitive files like cmdline, sched*, status are now protected against other users. As permission checking done in proc_pid_permission() and files' permissions are left untouched, programs expecting specific files' modes are not confused. hidepid=2 means hidepid=1 plus all /proc/PID/ will be invisible to other users. It doesn't mean that it hides whether a process exists (it can be learned by other means, e.g. by kill -0 $PID), but it hides process' euid and egid. It compicates intruder's task of gathering info about running processes, whether some daemon runs with elevated privileges, whether another user runs some sensitive program, whether other users run any program at all, etc. gid=XXX defines a group that will be able to gather all processes' info (as in hidepid=0 mode). This group should be used instead of putting nonroot user in sudoers file or something. However, untrusted users (like daemons, etc.) which are not supposed to monitor the tasks in the whole system should not be added to the group. hidepid=1 or higher is designed to restrict access to procfs files, which might reveal some sensitive private information like precise keystrokes timings: http://www.openwall.com/lists/oss-security/2011/11/05/3 hidepid=1/2 doesn't break monitoring userspace tools. ps, top, pgrep, and conky gracefully handle EPERM/ENOENT and behave as if the current user is the only user running processes. pstree shows the process subtree which contains "pstree" process. Note: the patch doesn't deal with setuid/setgid issues of keeping preopened descriptors of procfs files (like https://lkml.org/lkml/2011/2/7/368). We rely on that the leaked information like the scheduling counters of setuid apps doesn't threaten anybody's privacy - only the user started the setuid program may read the counters. Signed-off-by: Vasiliy Kulikov <segoon@openwall.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Greg KH <greg@kroah.com> Cc: Theodore Tso <tytso@MIT.EDU> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: James Morris <jmorris@namei.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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if (pid->hide_pid != 0)
seq_printf(seq, ",hidepid=%u", pid->hide_pid);
return 0;
}
static const struct super_operations proc_sops = {
.alloc_inode = proc_alloc_inode,
.destroy_inode = proc_destroy_inode,
.drop_inode = generic_delete_inode,
.evict_inode = proc_evict_inode,
.statfs = simple_statfs,
.remount_fs = proc_remount,
.show_options = proc_show_options,
};
enum {BIAS = -1U<<31};
static inline int use_pde(struct proc_dir_entry *pde)
{
return atomic_inc_unless_negative(&pde->in_use);
}
static void unuse_pde(struct proc_dir_entry *pde)
{
if (atomic_dec_return(&pde->in_use) == BIAS)
complete(pde->pde_unload_completion);
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}
/* pde is locked */
static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
{
if (pdeo->closing) {
/* somebody else is doing that, just wait */
DECLARE_COMPLETION_ONSTACK(c);
pdeo->c = &c;
spin_unlock(&pde->pde_unload_lock);
wait_for_completion(&c);
spin_lock(&pde->pde_unload_lock);
} else {
struct file *file;
pdeo->closing = 1;
spin_unlock(&pde->pde_unload_lock);
file = pdeo->file;
pde->proc_fops->release(file_inode(file), file);
spin_lock(&pde->pde_unload_lock);
list_del(&pdeo->lh);
if (pdeo->c)
complete(pdeo->c);
kfree(pdeo);
}
}
void proc_entry_rundown(struct proc_dir_entry *de)
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{
DECLARE_COMPLETION_ONSTACK(c);
/* Wait until all existing callers into module are done. */
de->pde_unload_completion = &c;
if (atomic_add_return(BIAS, &de->in_use) != BIAS)
wait_for_completion(&c);
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spin_lock(&de->pde_unload_lock);
while (!list_empty(&de->pde_openers)) {
struct pde_opener *pdeo;
pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
close_pdeo(de, pdeo);
}
spin_unlock(&de->pde_unload_lock);
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}
static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
loff_t rv = -EINVAL;
if (use_pde(pde)) {
loff_t (*llseek)(struct file *, loff_t, int);
llseek = pde->proc_fops->llseek;
if (!llseek)
llseek = default_llseek;
rv = llseek(file, offset, whence);
unuse_pde(pde);
}
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return rv;
}
static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
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{
ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
struct proc_dir_entry *pde = PDE(file_inode(file));
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ssize_t rv = -EIO;
if (use_pde(pde)) {
read = pde->proc_fops->read;
if (read)
rv = read(file, buf, count, ppos);
unuse_pde(pde);
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}
return rv;
}
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static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
struct proc_dir_entry *pde = PDE(file_inode(file));
ssize_t rv = -EIO;
if (use_pde(pde)) {
write = pde->proc_fops->write;
if (write)
rv = write(file, buf, count, ppos);
unuse_pde(pde);
}
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return rv;
}
static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
unsigned int rv = DEFAULT_POLLMASK;
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unsigned int (*poll)(struct file *, struct poll_table_struct *);
if (use_pde(pde)) {
poll = pde->proc_fops->poll;
if (poll)
rv = poll(file, pts);
unuse_pde(pde);
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}
return rv;
}
static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
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long rv = -ENOTTY;
long (*ioctl)(struct file *, unsigned int, unsigned long);
if (use_pde(pde)) {
ioctl = pde->proc_fops->unlocked_ioctl;
if (ioctl)
rv = ioctl(file, cmd, arg);
unuse_pde(pde);
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}
return rv;
}
#ifdef CONFIG_COMPAT
static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
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long rv = -ENOTTY;
long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
if (use_pde(pde)) {
compat_ioctl = pde->proc_fops->compat_ioctl;
if (compat_ioctl)
rv = compat_ioctl(file, cmd, arg);
unuse_pde(pde);
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}
return rv;
}
#endif
static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
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int rv = -EIO;
int (*mmap)(struct file *, struct vm_area_struct *);
if (use_pde(pde)) {
mmap = pde->proc_fops->mmap;
if (mmap)
rv = mmap(file, vma);
unuse_pde(pde);
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}
return rv;
}
static unsigned long
proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
unsigned long rv = -EIO;
if (use_pde(pde)) {
typeof(proc_reg_get_unmapped_area) *get_area;
get_area = pde->proc_fops->get_unmapped_area;
#ifdef CONFIG_MMU
if (!get_area)
get_area = current->mm->get_unmapped_area;
#endif
if (get_area)
rv = get_area(file, orig_addr, len, pgoff, flags);
else
rv = orig_addr;
unuse_pde(pde);
}
return rv;
}
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static int proc_reg_open(struct inode *inode, struct file *file)
{
struct proc_dir_entry *pde = PDE(inode);
int rv = 0;
int (*open)(struct inode *, struct file *);
int (*release)(struct inode *, struct file *);
struct pde_opener *pdeo;
/*
* What for, you ask? Well, we can have open, rmmod, remove_proc_entry
* sequence. ->release won't be called because ->proc_fops will be
* cleared. Depending on complexity of ->release, consequences vary.
*
* We can't wait for mercy when close will be done for real, it's
* deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
* by hand in remove_proc_entry(). For this, save opener's credentials
* for later.
*/
pdeo = kzalloc(sizeof(struct pde_opener), GFP_KERNEL);
if (!pdeo)
return -ENOMEM;
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if (!use_pde(pde)) {
kfree(pdeo);
return -ENOENT;
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}
open = pde->proc_fops->open;
release = pde->proc_fops->release;
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if (open)
rv = open(inode, file);
if (rv == 0 && release) {
/* To know what to release. */
pdeo->file = file;
/* Strictly for "too late" ->release in proc_reg_release(). */
spin_lock(&pde->pde_unload_lock);
list_add(&pdeo->lh, &pde->pde_openers);
spin_unlock(&pde->pde_unload_lock);
} else
kfree(pdeo);
unuse_pde(pde);
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return rv;
}
static int proc_reg_release(struct inode *inode, struct file *file)
{
struct proc_dir_entry *pde = PDE(inode);
struct pde_opener *pdeo;
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spin_lock(&pde->pde_unload_lock);
list_for_each_entry(pdeo, &pde->pde_openers, lh) {
if (pdeo->file == file) {
close_pdeo(pde, pdeo);
break;
}
}
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spin_unlock(&pde->pde_unload_lock);
return 0;
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}
static const struct file_operations proc_reg_file_ops = {
.llseek = proc_reg_llseek,
.read = proc_reg_read,
.write = proc_reg_write,
.poll = proc_reg_poll,
.unlocked_ioctl = proc_reg_unlocked_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = proc_reg_compat_ioctl,
#endif
.mmap = proc_reg_mmap,
.get_unmapped_area = proc_reg_get_unmapped_area,
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.open = proc_reg_open,
.release = proc_reg_release,
};
#ifdef CONFIG_COMPAT
static const struct file_operations proc_reg_file_ops_no_compat = {
.llseek = proc_reg_llseek,
.read = proc_reg_read,
.write = proc_reg_write,
.poll = proc_reg_poll,
.unlocked_ioctl = proc_reg_unlocked_ioctl,
.mmap = proc_reg_mmap,
.get_unmapped_area = proc_reg_get_unmapped_area,
.open = proc_reg_open,
.release = proc_reg_release,
};
#endif
static void proc_put_link(void *p)
{
unuse_pde(p);
}
static const char *proc_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
struct proc_dir_entry *pde = PDE(inode);
if (unlikely(!use_pde(pde)))
return ERR_PTR(-EINVAL);
set_delayed_call(done, proc_put_link, pde);
return pde->data;
}
const struct inode_operations proc_link_inode_operations = {
.readlink = generic_readlink,
.get_link = proc_get_link,
};
struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
{
struct inode *inode = new_inode_pseudo(sb);
if (inode) {
inode->i_ino = de->low_ino;
inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
PROC_I(inode)->pde = de;
if (is_empty_pde(de)) {
make_empty_dir_inode(inode);
return inode;
}
if (de->mode) {
inode->i_mode = de->mode;
inode->i_uid = de->uid;
inode->i_gid = de->gid;
}
if (de->size)
inode->i_size = de->size;
if (de->nlink)
set_nlink(inode, de->nlink);
WARN_ON(!de->proc_iops);
inode->i_op = de->proc_iops;
if (de->proc_fops) {
if (S_ISREG(inode->i_mode)) {
#ifdef CONFIG_COMPAT
if (!de->proc_fops->compat_ioctl)
inode->i_fop =
&proc_reg_file_ops_no_compat;
else
#endif
inode->i_fop = &proc_reg_file_ops;
} else {
inode->i_fop = de->proc_fops;
}
2007-07-16 06:39:00 +00:00
}
} else
pde_put(de);
return inode;
}
int proc_fill_super(struct super_block *s, void *data, int silent)
{
struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
struct inode *root_inode;
int ret;
if (!proc_parse_options(data, ns))
return -EINVAL;
/* User space would break if executables or devices appear on proc */
s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = PROC_SUPER_MAGIC;
s->s_op = &proc_sops;
s->s_time_gran = 1;
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull userns vfs updates from Eric Biederman: "This tree contains some very long awaited work on generalizing the user namespace support for mounting filesystems to include filesystems with a backing store. The real world target is fuse but the goal is to update the vfs to allow any filesystem to be supported. This patchset is based on a lot of code review and testing to approach that goal. While looking at what is needed to support the fuse filesystem it became clear that there were things like xattrs for security modules that needed special treatment. That the resolution of those concerns would not be fuse specific. That sorting out these general issues made most sense at the generic level, where the right people could be drawn into the conversation, and the issues could be solved for everyone. At a high level what this patchset does a couple of simple things: - Add a user namespace owner (s_user_ns) to struct super_block. - Teach the vfs to handle filesystem uids and gids not mapping into to kuids and kgids and being reported as INVALID_UID and INVALID_GID in vfs data structures. By assigning a user namespace owner filesystems that are mounted with only user namespace privilege can be detected. This allows security modules and the like to know which mounts may not be trusted. This also allows the set of uids and gids that are communicated to the filesystem to be capped at the set of kuids and kgids that are in the owning user namespace of the filesystem. One of the crazier corner casees this handles is the case of inodes whose i_uid or i_gid are not mapped into the vfs. Most of the code simply doesn't care but it is easy to confuse the inode writeback path so no operation that could cause an inode write-back is permitted for such inodes (aka only reads are allowed). This set of changes starts out by cleaning up the code paths involved in user namespace permirted mounts. Then when things are clean enough adds code that cleanly sets s_user_ns. Then additional restrictions are added that are possible now that the filesystem superblock contains owner information. These changes should not affect anyone in practice, but there are some parts of these restrictions that are changes in behavior. - Andy's restriction on suid executables that does not honor the suid bit when the path is from another mount namespace (think /proc/[pid]/fd/) or when the filesystem was mounted by a less privileged user. - The replacement of the user namespace implicit setting of MNT_NODEV with implicitly setting SB_I_NODEV on the filesystem superblock instead. Using SB_I_NODEV is a stronger form that happens to make this state user invisible. The user visibility can be managed but it caused problems when it was introduced from applications reasonably expecting mount flags to be what they were set to. There is a little bit of work remaining before it is safe to support mounting filesystems with backing store in user namespaces, beyond what is in this set of changes. - Verifying the mounter has permission to read/write the block device during mount. - Teaching the integrity modules IMA and EVM to handle filesystems mounted with only user namespace root and to reduce trust in their security xattrs accordingly. - Capturing the mounters credentials and using that for permission checks in d_automount and the like. (Given that overlayfs already does this, and we need the work in d_automount it make sense to generalize this case). Furthermore there are a few changes that are on the wishlist: - Get all filesystems supporting posix acls using the generic posix acls so that posix_acl_fix_xattr_from_user and posix_acl_fix_xattr_to_user may be removed. [Maintainability] - Reducing the permission checks in places such as remount to allow the superblock owner to perform them. - Allowing the superblock owner to chown files with unmapped uids and gids to something that is mapped so the files may be treated normally. I am not considering even obvious relaxations of permission checks until it is clear there are no more corner cases that need to be locked down and handled generically. Many thanks to Seth Forshee who kept this code alive, and putting up with me rewriting substantial portions of what he did to handle more corner cases, and for his diligent testing and reviewing of my changes" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (30 commits) fs: Call d_automount with the filesystems creds fs: Update i_[ug]id_(read|write) to translate relative to s_user_ns evm: Translate user/group ids relative to s_user_ns when computing HMAC dquot: For now explicitly don't support filesystems outside of init_user_ns quota: Handle quota data stored in s_user_ns in quota_setxquota quota: Ensure qids map to the filesystem vfs: Don't create inodes with a uid or gid unknown to the vfs vfs: Don't modify inodes with a uid or gid unknown to the vfs cred: Reject inodes with invalid ids in set_create_file_as() fs: Check for invalid i_uid in may_follow_link() vfs: Verify acls are valid within superblock's s_user_ns. userns: Handle -1 in k[ug]id_has_mapping when !CONFIG_USER_NS fs: Refuse uid/gid changes which don't map into s_user_ns selinux: Add support for unprivileged mounts from user namespaces Smack: Handle labels consistently in untrusted mounts Smack: Add support for unprivileged mounts from user namespaces fs: Treat foreign mounts as nosuid fs: Limit file caps to the user namespace of the super block userns: Remove the now unnecessary FS_USERNS_DEV_MOUNT flag userns: Remove implicit MNT_NODEV fragility. ...
2016-07-29 22:54:19 +00:00
/*
* procfs isn't actually a stacking filesystem; however, there is
* too much magic going on inside it to permit stacking things on
* top of it
*/
s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
pde_get(&proc_root);
root_inode = proc_get_inode(s, &proc_root);
if (!root_inode) {
pr_err("proc_fill_super: get root inode failed\n");
return -ENOMEM;
}
s->s_root = d_make_root(root_inode);
if (!s->s_root) {
pr_err("proc_fill_super: allocate dentry failed\n");
return -ENOMEM;
}
ret = proc_setup_self(s);
if (ret) {
return ret;
}
return proc_setup_thread_self(s);
}