Commit Graph

424 Commits

Author SHA1 Message Date
Eric W. Biederman
da362b09e4 umount: Do not allow unmounting rootfs.
Andrew Vagin <avagin@parallels.com> writes:

> #define _GNU_SOURCE
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <sched.h>
> #include <unistd.h>
> #include <sys/mount.h>
>
> int main(int argc, char **argv)
> {
> 	int fd;
>
> 	fd = open("/proc/self/ns/mnt", O_RDONLY);
> 	if (fd < 0)
> 	   return 1;
> 	   while (1) {
> 	   	 if (umount2("/", MNT_DETACH) ||
> 		        setns(fd, CLONE_NEWNS))
> 					break;
> 					}
>
> 					return 0;
> }
>
> root@ubuntu:/home/avagin# gcc -Wall nsenter.c -o nsenter
> root@ubuntu:/home/avagin# strace ./nsenter
> execve("./nsenter", ["./nsenter"], [/* 22 vars */]) = 0
> ...
> open("/proc/self/ns/mnt", O_RDONLY)     = 3
> umount("/", MNT_DETACH)                 = 0
> setns(3, 131072)                        = 0
> umount("/", MNT_DETACH
>
causes:

> [  260.548301] ------------[ cut here ]------------
> [  260.550941] kernel BUG at /build/buildd/linux-3.13.0/fs/pnode.c:372!
> [  260.552068] invalid opcode: 0000 [#1] SMP
> [  260.552068] Modules linked in: xt_CHECKSUM iptable_mangle xt_tcpudp xt_addrtype xt_conntrack ipt_MASQUERADE iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack bridge stp llc dm_thin_pool dm_persistent_data dm_bufio dm_bio_prison iptable_filter ip_tables x_tables crct10dif_pclmul crc32_pclmul ghash_clmulni_intel binfmt_misc nfsd auth_rpcgss nfs_acl aesni_intel nfs lockd aes_x86_64 sunrpc fscache lrw gf128mul glue_helper ablk_helper cryptd serio_raw ppdev parport_pc lp parport btrfs xor raid6_pq libcrc32c psmouse floppy
> [  260.552068] CPU: 0 PID: 1723 Comm: nsenter Not tainted 3.13.0-30-generic #55-Ubuntu
> [  260.552068] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> [  260.552068] task: ffff8800376097f0 ti: ffff880074824000 task.ti: ffff880074824000
> [  260.552068] RIP: 0010:[<ffffffff811e9483>]  [<ffffffff811e9483>] propagate_umount+0x123/0x130
> [  260.552068] RSP: 0018:ffff880074825e98  EFLAGS: 00010246
> [  260.552068] RAX: ffff88007c741140 RBX: 0000000000000002 RCX: ffff88007c741190
> [  260.552068] RDX: ffff88007c741190 RSI: ffff880074825ec0 RDI: ffff880074825ec0
> [  260.552068] RBP: ffff880074825eb0 R08: 00000000000172e0 R09: ffff88007fc172e0
> [  260.552068] R10: ffffffff811cc642 R11: ffffea0001d59000 R12: ffff88007c741140
> [  260.552068] R13: ffff88007c741140 R14: ffff88007c741140 R15: 0000000000000000
> [  260.552068] FS:  00007fd5c7e41740(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
> [  260.552068] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  260.552068] CR2: 00007fd5c7968050 CR3: 0000000070124000 CR4: 00000000000406f0
> [  260.552068] Stack:
> [  260.552068]  0000000000000002 0000000000000002 ffff88007c631000 ffff880074825ed8
> [  260.552068]  ffffffff811dcfac ffff88007c741140 0000000000000002 ffff88007c741160
> [  260.552068]  ffff880074825f38 ffffffff811dd12b ffffffff811cc642 0000000075640000
> [  260.552068] Call Trace:
> [  260.552068]  [<ffffffff811dcfac>] umount_tree+0x20c/0x260
> [  260.552068]  [<ffffffff811dd12b>] do_umount+0x12b/0x300
> [  260.552068]  [<ffffffff811cc642>] ? final_putname+0x22/0x50
> [  260.552068]  [<ffffffff811cc849>] ? putname+0x29/0x40
> [  260.552068]  [<ffffffff811dd88c>] SyS_umount+0xdc/0x100
> [  260.552068]  [<ffffffff8172aeff>] tracesys+0xe1/0xe6
> [  260.552068] Code: 89 50 08 48 8b 50 08 48 89 02 49 89 45 08 e9 72 ff ff ff 0f 1f 44 00 00 4c 89 e6 4c 89 e7 e8 f5 f6 ff ff 48 89 c3 e9 39 ff ff ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 66 66 66 66 90 55 b8 01
> [  260.552068] RIP  [<ffffffff811e9483>] propagate_umount+0x123/0x130
> [  260.552068]  RSP <ffff880074825e98>
> [  260.611451] ---[ end trace 11c33d85f1d4c652 ]--

Which in practice is totally uninteresting.  Only the global root user can
do it, and it is just a stupid thing to do.

However that is no excuse to allow a silly way to oops the kernel.

We can avoid this silly problem by setting MNT_LOCKED on the rootfs
mount point and thus avoid needing any special cases in the unmount
code.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-12-02 10:46:49 -06:00
Eric W. Biederman
b2f5d4dc38 umount: Disallow unprivileged mount force
Forced unmount affects not just the mount namespace but the underlying
superblock as well.  Restrict forced unmount to the global root user
for now.  Otherwise it becomes possible a user in a less privileged
mount namespace to force the shutdown of a superblock of a filesystem
in a more privileged mount namespace, allowing a DOS attack on root.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-12-02 10:46:48 -06:00
Eric W. Biederman
3e1866410f mnt: Implicitly add MNT_NODEV on remount when it was implicitly added by mount
Now that remount is properly enforcing the rule that you can't remove
nodev at least sandstorm.io is breaking when performing a remount.

It turns out that there is an easy intuitive solution implicitly
add nodev on remount when nodev was implicitly added on mount.

Tested-by: Cedric Bosdonnat <cbosdonnat@suse.com>
Tested-by: Richard Weinberger <richard@nod.at>
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-12-02 10:46:39 -06:00
Miklos Szeredi
c771d683a6 vfs: introduce clone_private_mount()
Overlayfs needs a private clone of the mount, so create a function for
this and export to modules.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
2014-10-24 00:14:36 +02:00
Linus Torvalds
ce9d7f7b45 Merge branch 'CVE-2014-7970' of git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux
Pull pivot_root() fix from Andy Lutomirski.

Prevent a leak of unreachable mounts.

* 'CVE-2014-7970' of git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux:
  mnt: Prevent pivot_root from creating a loop in the mount tree
2014-10-15 06:43:27 +02:00
Eric W. Biederman
0d0826019e mnt: Prevent pivot_root from creating a loop in the mount tree
Andy Lutomirski recently demonstrated that when chroot is used to set
the root path below the path for the new ``root'' passed to pivot_root
the pivot_root system call succeeds and leaks mounts.

In examining the code I see that starting with a new root that is
below the current root in the mount tree will result in a loop in the
mount tree after the mounts are detached and then reattached to one
another.  Resulting in all kinds of ugliness including a leak of that
mounts involved in the leak of the mount loop.

Prevent this problem by ensuring that the new mount is reachable from
the current root of the mount tree.

[Added stable cc.  Fixes CVE-2014-7970.  --Andy]

Cc: stable@vger.kernel.org
Reported-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/87bnpmihks.fsf@x220.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
2014-10-14 14:27:19 -07:00
Linus Torvalds
0ef3a56b1c Merge branch 'CVE-2014-7975' of git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux
Pull do_umount fix from Andy Lutomirski:
 "This fix really ought to be safe.  Inside a mountns owned by a
  non-root user namespace, the namespace root almost always has
  MNT_LOCKED set (if it doesn't, then there's a bug, because rootfs
  could be exposed).  In that case, calling umount on "/" will return
  -EINVAL with or without this patch.

  Outside a userns, this patch will have no effect.  may_mount, required
  by umount, already checks
     ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)
  so an additional capable(CAP_SYS_ADMIN) check will have no effect.

  That leaves anything that calls umount on "/" in a non-root userns
  while chrooted.  This is the case that is currently broken (it
  remounts ro, which shouldn't be allowed) and that my patch changes to
  -EPERM.  If anything relies on *that*, I'd be surprised"

* 'CVE-2014-7975' of git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux:
  fs: Add a missing permission check to do_umount
2014-10-14 08:35:01 +02:00
Seunghun Lee
5e6123f347 vfs: move getname() from callers to do_mount()
It would make more sense to pass char __user * instead of
char * in callers of do_mount() and do getname() inside do_mount().

Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Seunghun Lee <waydi1@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:39:16 -04:00
Tim Gardner
b8850d1fa8 fs: namespace: suppress 'may be used uninitialized' warnings
The gcc version 4.9.1 compiler complains Even though it isn't possible for
these variables to not get initialized before they are used.

fs/namespace.c: In function ‘SyS_mount’:
fs/namespace.c:2720:8: warning: ‘kernel_dev’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
        ^
fs/namespace.c:2699:8: note: ‘kernel_dev’ was declared here
  char *kernel_dev;
        ^
fs/namespace.c:2720:8: warning: ‘kernel_type’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
        ^
fs/namespace.c:2697:8: note: ‘kernel_type’ was declared here
  char *kernel_type;
        ^

Fix the warnings by simplifying copy_mount_string() as suggested by Al Viro.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:39:10 -04:00
Eric W. Biederman
80b5dce8c5 vfs: Add a function to lazily unmount all mounts from any dentry.
The new function detach_mounts comes in two pieces.  The first piece
is a static inline test of d_mounpoint that returns immediately
without taking any locks if d_mounpoint is not set.  In the common
case when mountpoints are absent this allows the vfs to continue
running with it's same cacheline foot print.

The second piece of detach_mounts __detach_mounts actually does the
work and it assumes that a mountpoint is present so it is slow and
takes namespace_sem for write, and then locks the mount hash (aka
mount_lock) after a struct mountpoint has been found.

With those two locks held each entry on the list of mounts on a
mountpoint is selected and lazily unmounted until all of the mount
have been lazily unmounted.

v7: Wrote a proper change description and removed the changelog
    documenting deleted wrong turns.

Signed-off-by: Eric W. Biederman <ebiederman@twitter.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:38:55 -04:00
Eric W. Biederman
e2dfa93546 vfs: factor out lookup_mountpoint from new_mountpoint
I am shortly going to add a new user of struct mountpoint that
needs to look up existing entries but does not want to create
a struct mountpoint if one does not exist.  Therefore to keep
the code simple and easy to read split out lookup_mountpoint
from new_mountpoint.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:38:55 -04:00
Eric W. Biederman
0a5eb7c818 vfs: Keep a list of mounts on a mount point
To spot any possible problems call BUG if a mountpoint
is put when it's list of mounts is not empty.

AV: use hlist instead of list_head

Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Eric W. Biederman <ebiederman@twitter.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:38:54 -04:00
Eric W. Biederman
7af1364ffa vfs: Don't allow overwriting mounts in the current mount namespace
In preparation for allowing mountpoints to be renamed and unlinked
in remote filesystems and in other mount namespaces test if on a dentry
there is a mount in the local mount namespace before allowing it to
be renamed or unlinked.

The primary motivation here are old versions of fusermount unmount
which is not safe if the a path can be renamed or unlinked while it is
verifying the mount is safe to unmount.  More recent versions are simpler
and safer by simply using UMOUNT_NOFOLLOW when unmounting a mount
in a directory owned by an arbitrary user.

Miklos Szeredi <miklos@szeredi.hu> reports this is approach is good
enough to remove concerns about new kernels mixed with old versions
of fusermount.

A secondary motivation for restrictions here is that it removing empty
directories that have non-empty mount points on them appears to
violate the rule that rmdir can not remove empty directories.  As
Linus Torvalds pointed out this is useful for programs (like git) that
test if a directory is empty with rmdir.

Therefore this patch arranges to enforce the existing mount point
semantics for local mount namespace.

v2: Rewrote the test to be a drop in replacement for d_mountpoint
v3: Use bool instead of int as the return type of is_local_mountpoint

Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:38:54 -04:00
Al Viro
9ea459e110 delayed mntput
On final mntput() we want fs shutdown to happen before return to
userland; however, the only case where we want it happen right
there (i.e. where task_work_add won't do) is MNT_INTERNAL victim.
Those have to be fully synchronous - failure halfway through module
init might count on having vfsmount killed right there.  Fortunately,
final mntput on MNT_INTERNAL vfsmounts happens on shallow stack.
So we handle those synchronously and do an analog of delayed fput
logics for everything else.

As the result, we are guaranteed that fs shutdown will always happen
on shallow stack.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:38:53 -04:00
Andy Lutomirski
a1480dcc3c fs: Add a missing permission check to do_umount
Accessing do_remount_sb should require global CAP_SYS_ADMIN, but
only one of the two call sites was appropriately protected.

Fixes CVE-2014-7975.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
2014-10-08 12:32:47 -07:00
Al Viro
81b6b06197 fix EBUSY on umount() from MNT_SHRINKABLE
We need the parents of victims alive until namespace_unlock() gets to
dput() of the (ex-)mountpoints.  However, that screws up the "is it
busy" checks in case when we have shrinkable mounts that need to be
killed.  Solution: go ahead and decrement refcounts of parents right
in umount_tree(), increment them again just before dropping rwsem in
namespace_unlock() (and let the loop in the end of namespace_unlock()
finally drop those references for good, as we do now).  Parents can't
get freed until we drop rwsem - at least one reference is kept until
then, both in case when parent is among the victims and when it is
not.  So they'll still be around when we get to namespace_unlock().

Cc: stable@vger.kernel.org # 3.12+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-08-30 18:32:05 -04:00
Al Viro
88b368f27a get rid of propagate_umount() mistakenly treating slaves as busy.
The check in __propagate_umount() ("has somebody explicitly mounted
something on that slave?") is done *before* taking the already doomed
victims out of the child lists.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-08-30 18:31:41 -04:00
Linus Torvalds
f6f993328b Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs updates from Al Viro:
 "Stuff in here:

   - acct.c fixes and general rework of mnt_pin mechanism.  That allows
     to go for delayed-mntput stuff, which will permit mntput() on deep
     stack without worrying about stack overflows - fs shutdown will
     happen on shallow stack.  IOW, we can do Eric's umount-on-rmdir
     series without introducing tons of stack overflows on new mntput()
     call chains it introduces.
   - Bruce's d_splice_alias() patches
   - more Miklos' rename() stuff.
   - a couple of regression fixes (stable fodder, in the end of branch)
     and a fix for API idiocy in iov_iter.c.

  There definitely will be another pile, maybe even two.  I'd like to
  get Eric's series in this time, but even if we miss it, it'll go right
  in the beginning of for-next in the next cycle - the tricky part of
  prereqs is in this pile"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits)
  fix copy_tree() regression
  __generic_file_write_iter(): fix handling of sync error after DIO
  switch iov_iter_get_pages() to passing maximal number of pages
  fs: mark __d_obtain_alias static
  dcache: d_splice_alias should detect loops
  exportfs: update Exporting documentation
  dcache: d_find_alias needn't recheck IS_ROOT && DCACHE_DISCONNECTED
  dcache: remove unused d_find_alias parameter
  dcache: d_obtain_alias callers don't all want DISCONNECTED
  dcache: d_splice_alias should ignore DCACHE_DISCONNECTED
  dcache: d_splice_alias mustn't create directory aliases
  dcache: close d_move race in d_splice_alias
  dcache: move d_splice_alias
  namei: trivial fix to vfs_rename_dir comment
  VFS: allow ->d_manage() to declare -EISDIR in rcu_walk mode.
  cifs: support RENAME_NOREPLACE
  hostfs: support rename flags
  shmem: support RENAME_EXCHANGE
  shmem: support RENAME_NOREPLACE
  btrfs: add RENAME_NOREPLACE
  ...
2014-08-11 11:44:11 -07:00
Al Viro
12a5b5294c fix copy_tree() regression
Since 3.14 we had copy_tree() get the shadowing wrong - if we had one
vfsmount shadowing another (i.e. if A is a slave of B, C is mounted
on A/foo, then D got mounted on B/foo creating D' on A/foo shadowed
by C), copy_tree() of A would make a copy of D' shadow the the copy of
C, not the other way around.

It's easy to fix, fortunately - just make sure that mount follows
the one that shadows it in mnt_child as well as in mnt_hash, and when
copy_tree() decides to attach a new mount, check if the last child
it has added to the same parent should be shadowing the new one.
And if it should, just use the same logics commit_tree() has - put the
new mount into the hash and children lists right after the one that
should shadow it.

Cc: stable@vger.kernel.org [3.14 and later]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-08-11 12:28:10 -04:00
Linus Torvalds
77e40aae76 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace updates from Eric Biederman:
 "This is a bunch of small changes built against 3.16-rc6.  The most
  significant change for users is the first patch which makes setns
  drmatically faster by removing unneded rcu handling.

  The next chunk of changes are so that "mount -o remount,.." will not
  allow the user namespace root to drop flags on a mount set by the
  system wide root.  Aks this forces read-only mounts to stay read-only,
  no-dev mounts to stay no-dev, no-suid mounts to stay no-suid, no-exec
  mounts to stay no exec and it prevents unprivileged users from messing
  with a mounts atime settings.  I have included my test case as the
  last patch in this series so people performing backports can verify
  this change works correctly.

  The next change fixes a bug in NFS that was discovered while auditing
  nsproxy users for the first optimization.  Today you can oops the
  kernel by reading /proc/fs/nfsfs/{servers,volumes} if you are clever
  with pid namespaces.  I rebased and fixed the build of the
  !CONFIG_NFS_FS case yesterday when a build bot caught my typo.  Given
  that no one to my knowledge bases anything on my tree fixing the typo
  in place seems more responsible that requiring a typo-fix to be
  backported as well.

  The last change is a small semantic cleanup introducing
  /proc/thread-self and pointing /proc/mounts and /proc/net at it.  This
  prevents several kinds of problemantic corner cases.  It is a
  user-visible change so it has a minute chance of causing regressions
  so the change to /proc/mounts and /proc/net are individual one line
  commits that can be trivially reverted.  Unfortunately I lost and
  could not find the email of the original reporter so he is not
  credited.  From at least one perspective this change to /proc/net is a
  refgression fix to allow pthread /proc/net uses that were broken by
  the introduction of the network namespace"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  proc: Point /proc/mounts at /proc/thread-self/mounts instead of /proc/self/mounts
  proc: Point /proc/net at /proc/thread-self/net instead of /proc/self/net
  proc: Implement /proc/thread-self to point at the directory of the current thread
  proc: Have net show up under /proc/<tgid>/task/<tid>
  NFS: Fix /proc/fs/nfsfs/servers and /proc/fs/nfsfs/volumes
  mnt: Add tests for unprivileged remount cases that have found to be faulty
  mnt: Change the default remount atime from relatime to the existing value
  mnt: Correct permission checks in do_remount
  mnt: Move the test for MNT_LOCK_READONLY from change_mount_flags into do_remount
  mnt: Only change user settable mount flags in remount
  namespaces: Use task_lock and not rcu to protect nsproxy
2014-08-09 17:10:41 -07:00
Al Viro
3064c3563b death to mnt_pinned
Rather than playing silly buggers with vfsmount refcounts, just have
acct_on() ask fs/namespace.c for internal clone of file->f_path.mnt
and replace it with said clone.  Then attach the pin to original
vfsmount.  Voila - the clone will be alive until the file gets closed,
making sure that underlying superblock remains active, etc., and
we can drop the original vfsmount, so that it's not kept busy.
If the file lives until the final mntput of the original vfsmount,
we'll notice that there's an fs_pin (one in bsd_acct_struct that
holds that file) and mnt_pin_kill() will take it out.  Since
->kill() is synchronous, we won't proceed past that point until
these files are closed (and private clones of our vfsmount are
gone), so we get the same ordering warranties we used to get.

mnt_pin()/mnt_unpin()/->mnt_pinned is gone now, and good riddance -
it never became usable outside of kernel/acct.c (and racy wrt
umount even there).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-08-07 14:40:09 -04:00
Al Viro
8fa1f1c2bd make fs/{namespace,super}.c forget about acct.h
These externs belong in fs/internal.h.  Rename (they are not acct-specific
anymore) and move them over there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-08-07 14:40:09 -04:00
Al Viro
215752fce3 acct: get rid of acct_list
Put these suckers on per-vfsmount and per-superblock lists instead.
Note: right now it's still acct_lock for everything, but that's
going to change.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-08-07 14:40:08 -04:00
Ken Helias
1d023284c3 list: fix order of arguments for hlist_add_after(_rcu)
All other add functions for lists have the new item as first argument
and the position where it is added as second argument.  This was changed
for no good reason in this function and makes using it unnecessary
confusing.

The name was changed to hlist_add_behind() to cause unconverted code to
generate a compile error instead of using the wrong parameter order.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Ken Helias <kenhelias@firemail.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>	[intel driver bits]
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-06 18:01:24 -07:00
Eric W. Biederman
ffbc6f0ead mnt: Change the default remount atime from relatime to the existing value
Since March 2009 the kernel has treated the state that if no
MS_..ATIME flags are passed then the kernel defaults to relatime.

Defaulting to relatime instead of the existing atime state during a
remount is silly, and causes problems in practice for people who don't
specify any MS_...ATIME flags and to get the default filesystem atime
setting.  Those users may encounter a permission error because the
default atime setting does not work.

A default that does not work and causes permission problems is
ridiculous, so preserve the existing value to have a default
atime setting that is always guaranteed to work.

Using the default atime setting in this way is particularly
interesting for applications built to run in restricted userspace
environments without /proc mounted, as the existing atime mount
options of a filesystem can not be read from /proc/mounts.

In practice this fixes user space that uses the default atime
setting on remount that are broken by the permission checks
keeping less privileged users from changing more privileged users
atime settings.

Cc: stable@vger.kernel.org
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-07-31 17:12:59 -07:00
Eric W. Biederman
9566d67428 mnt: Correct permission checks in do_remount
While invesgiating the issue where in "mount --bind -oremount,ro ..."
would result in later "mount --bind -oremount,rw" succeeding even if
the mount started off locked I realized that there are several
additional mount flags that should be locked and are not.

In particular MNT_NOSUID, MNT_NODEV, MNT_NOEXEC, and the atime
flags in addition to MNT_READONLY should all be locked.  These
flags are all per superblock, can all be changed with MS_BIND,
and should not be changable if set by a more privileged user.

The following additions to the current logic are added in this patch.
- nosuid may not be clearable by a less privileged user.
- nodev  may not be clearable by a less privielged user.
- noexec may not be clearable by a less privileged user.
- atime flags may not be changeable by a less privileged user.

The logic with atime is that always setting atime on access is a
global policy and backup software and auditing software could break if
atime bits are not updated (when they are configured to be updated),
and serious performance degradation could result (DOS attack) if atime
updates happen when they have been explicitly disabled.  Therefore an
unprivileged user should not be able to mess with the atime bits set
by a more privileged user.

The additional restrictions are implemented with the addition of
MNT_LOCK_NOSUID, MNT_LOCK_NODEV, MNT_LOCK_NOEXEC, and MNT_LOCK_ATIME
mnt flags.

Taken together these changes and the fixes for MNT_LOCK_READONLY
should make it safe for an unprivileged user to create a user
namespace and to call "mount --bind -o remount,... ..." without
the danger of mount flags being changed maliciously.

Cc: stable@vger.kernel.org
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-07-31 17:12:34 -07:00
Eric W. Biederman
07b645589d mnt: Move the test for MNT_LOCK_READONLY from change_mount_flags into do_remount
There are no races as locked mount flags are guaranteed to never change.

Moving the test into do_remount makes it more visible, and ensures all
filesystem remounts pass the MNT_LOCK_READONLY permission check.  This
second case is not an issue today as filesystem remounts are guarded
by capable(CAP_DAC_ADMIN) and thus will always fail in less privileged
mount namespaces, but it could become an issue in the future.

Cc: stable@vger.kernel.org
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-07-31 17:12:17 -07:00
Eric W. Biederman
a6138db815 mnt: Only change user settable mount flags in remount
Kenton Varda <kenton@sandstorm.io> discovered that by remounting a
read-only bind mount read-only in a user namespace the
MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user
to the remount a read-only mount read-write.

Correct this by replacing the mask of mount flags to preserve
with a mask of mount flags that may be changed, and preserve
all others.   This ensures that any future bugs with this mask and
remount will fail in an easy to detect way where new mount flags
simply won't change.

Cc: stable@vger.kernel.org
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-07-31 17:11:54 -07:00
Eric W. Biederman
728dba3a39 namespaces: Use task_lock and not rcu to protect nsproxy
The synchronous syncrhonize_rcu in switch_task_namespaces makes setns
a sufficiently expensive system call that people have complained.

Upon inspect nsproxy no longer needs rcu protection for remote reads.
remote reads are rare.  So optimize for same process reads and write
by switching using rask_lock instead.

This yields a simpler to understand lock, and a faster setns system call.

In particular this fixes a performance regression observed
by Rafael David Tinoco <rafael.tinoco@canonical.com>.

This is effectively a revert of Pavel Emelyanov's commit
cf7b708c8d Make access to task's nsproxy lighter
from 2007.  The race this originialy fixed no longer exists as
do_notify_parent uses task_active_pid_ns(parent) instead of
parent->nsproxy.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2014-07-29 18:08:50 -07:00
David Howells
8ffcb32e05 VFS: Make delayed_free() call free_vfsmnt()
Make delayed_free() call free_vfsmnt() so that we don't have two functions
doing the same job.  This requires the calls to mnt_free_id() in free_vfsmnt()
to be moved into the callers of that function.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-04-01 23:19:18 -04:00
Al Viro
83f936c75e mark struct file that had write access grabbed by open()
new flag in ->f_mode - FMODE_WRITER.  Set by do_dentry_open() in case
when it has grabbed write access, checked by __fput() to decide whether
it wants to drop the sucker.  Allows to stop bothering with mnt_clone_write()
in alloc_file(), along with fewer special_file() checks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-04-01 23:19:12 -04:00
Al Viro
c7999c3627 reduce m_start() cost...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-04-01 23:19:09 -04:00
Al Viro
f2ebb3a921 smarter propagate_mnt()
The current mainline has copies propagated to *all* nodes, then
tears down the copies we made for nodes that do not contain
counterparts of the desired mountpoint.  That sets the right
propagation graph for the copies (at teardown time we move
the slaves of removed node to a surviving peer or directly
to master), but we end up paying a fairly steep price in
useless allocations.  It's fairly easy to create a situation
where N calls of mount(2) create exactly N bindings, with
O(N^2) vfsmounts allocated and freed in process.

Fortunately, it is possible to avoid those allocations/freeings.
The trick is to create copies in the right order and find which
one would've eventually become a master with the current algorithm.
It turns out to be possible in O(nodes getting propagation) time
and with no extra allocations at all.

One part is that we need to make sure that eventual master will be
created before its slaves, so we need to walk the propagation
tree in a different order - by peer groups.  And iterate through
the peers before dealing with the next group.

Another thing is finding the (earlier) copy that will be a master
of one we are about to create; to do that we are (temporary) marking
the masters of mountpoints we are attaching the copies to.

Either we are in a peer of the last mountpoint we'd dealt with,
or we have the following situation: we are attaching to mountpoint M,
the last copy S_0 had been attached to M_0 and there are sequences
S_0...S_n, M_0...M_n such that S_{i+1} is a master of S_{i},
S_{i} mounted on M{i} and we need to create a slave of the first S_{k}
such that M is getting propagation from M_{k}.  It means that the master
of M_{k} will be among the sequence of masters of M.  On the
other hand, the nearest marked node in that sequence will either
be the master of M_{k} or the master of M_{k-1} (the latter -
in the case if M_{k-1} is a slave of something M gets propagation
from, but in a wrong peer group).

So we go through the sequence of masters of M until we find
a marked one (P).  Let N be the one before it.  Then we go through
the sequence of masters of S_0 until we find one (say, S) mounted
on a node D that has P as master and check if D is a peer of N.
If it is, S will be the master of new copy, if not - the master of S
will be.

That's it for the hard part; the rest is fairly simple.  Iterator
is in next_group(), handling of one prospective mountpoint is
propagate_one().

It seems to survive all tests and gives a noticably better performance
than the current mainline for setups that are seriously using shared
subtrees.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-04-01 23:19:08 -04:00
Al Viro
38129a13e6 switch mnt_hash to hlist
fixes RCU bug - walking through hlist is safe in face of element moves,
since it's self-terminating.  Cyclic lists are not - if we end up jumping
to another hash chain, we'll loop infinitely without ever hitting the
original list head.

[fix for dumb braino folded]

Spotted by: Max Kellermann <mk@cm4all.com>
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-03-30 19:18:51 -04:00
Al Viro
0b1b901b5a don't bother with propagate_mnt() unless the target is shared
If the dest_mnt is not shared, propagate_mnt() does nothing -
there's no mounts to propagate to and thus no copies to create.
Might as well don't bother calling it in that case.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-03-30 19:18:50 -04:00
Al Viro
1d6a32acd7 keep shadowed vfsmounts together
preparation to switching mnt_hash to hlist

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-03-30 19:18:50 -04:00
Al Viro
0818bf27c0 resizable namespace.c hashes
* switch allocation to alloc_large_system_hash()
* make sizes overridable by boot parameters (mhash_entries=, mphash_entries=)
* switch mountpoint_hashtable from list_head to hlist_head

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-03-30 19:18:49 -04:00
Linus Torvalds
d3bad75a6d Driver core / sysfs patches for 3.14-rc1
Here's the big driver core and sysfs patch set for 3.14-rc1.
 
 There's a lot of work here moving sysfs logic out into a "kernfs" to
 allow other subsystems to also have a virtual filesystem with the same
 attributes of sysfs (handle device disconnect, dynamic creation /
 removal  as needed / unneeded, etc.  This is primarily being done for
 the cgroups filesystem, but the goal is to also move debugfs to it when
 it is ready, solving all of the known issues in that filesystem as well.
 The code isn't completed yet, but all should be stable now (there is a
 big section that was reverted due to problems found when testing.)
 
 There's also some other smaller fixes, and a driver core addition that
 allows for a "collection" of objects, that the DRM people will be using
 soon (it's in this tree to make merges after -rc1 easier.)
 
 All of this has been in linux-next with no reported issues.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-3.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core / sysfs patches from Greg KH:
 "Here's the big driver core and sysfs patch set for 3.14-rc1.

  There's a lot of work here moving sysfs logic out into a "kernfs" to
  allow other subsystems to also have a virtual filesystem with the same
  attributes of sysfs (handle device disconnect, dynamic creation /
  removal as needed / unneeded, etc)

  This is primarily being done for the cgroups filesystem, but the goal
  is to also move debugfs to it when it is ready, solving all of the
  known issues in that filesystem as well.  The code isn't completed
  yet, but all should be stable now (there is a big section that was
  reverted due to problems found when testing)

  There's also some other smaller fixes, and a driver core addition that
  allows for a "collection" of objects, that the DRM people will be
  using soon (it's in this tree to make merges after -rc1 easier)

  All of this has been in linux-next with no reported issues"

* tag 'driver-core-3.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (113 commits)
  kernfs: associate a new kernfs_node with its parent on creation
  kernfs: add struct dentry declaration in kernfs.h
  kernfs: fix get_active failure handling in kernfs_seq_*()
  Revert "kernfs: fix get_active failure handling in kernfs_seq_*()"
  Revert "kernfs: replace kernfs_node->u.completion with kernfs_root->deactivate_waitq"
  Revert "kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep()"
  Revert "kernfs: remove KERNFS_REMOVED"
  Revert "kernfs: restructure removal path to fix possible premature return"
  Revert "kernfs: invoke kernfs_unmap_bin_file() directly from __kernfs_remove()"
  Revert "kernfs: remove kernfs_addrm_cxt"
  Revert "kernfs: make kernfs_get_active() block if the node is deactivated but not removed"
  Revert "kernfs: implement kernfs_{de|re}activate[_self]()"
  Revert "kernfs, sysfs, driver-core: implement kernfs_remove_self() and its wrappers"
  Revert "pci: use device_remove_file_self() instead of device_schedule_callback()"
  Revert "scsi: use device_remove_file_self() instead of device_schedule_callback()"
  Revert "s390: use device_remove_file_self() instead of device_schedule_callback()"
  Revert "sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()"
  Revert "kernfs: remove unnecessary NULL check in __kernfs_remove()"
  kernfs: remove unnecessary NULL check in __kernfs_remove()
  drivers/base: provide an infrastructure for componentised subsystems
  ...
2014-01-20 15:49:44 -08:00
Tejun Heo
4b93dc9b1c sysfs, kernfs: prepare mount path for kernfs
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly.  This patch
rearranges mount path so that the kernfs and sysfs parts are separate.

* As sysfs_super_info won't be visible outside kernfs proper,
  kernfs_super_ns() is added to allow kernfs users to access a
  super_block's namespace tag.

* Generic mount operation is separated out into kernfs_mount_ns().
  sysfs_mount() now just performs sysfs-specific permission check,
  acquires namespace tag, and invokes kernfs_mount_ns().

* Generic superblock release is separated out into kernfs_kill_sb()
  which can be used directly as file_system_type->kill_sb().  As sysfs
  needs to put the namespace tag, sysfs_kill_sb() wraps
  kernfs_kill_sb() with ns tag put.

* sysfs_dir_cachep init and sysfs_inode_init() are separated out into
  kernfs_init().  kernfs_init() uses only small amount of memory and
  trying to handle and propagate kernfs_init() failure doesn't make
  much sense.  Use SLAB_PANIC for sysfs_dir_cachep and make
  sysfs_inode_init() panic on failure.

  After this change, kernfs_init() should be called before
  sysfs_init(), fs/namespace.c::mnt_init() modified accordingly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-11-29 18:16:08 -08:00
Eric W. Biederman
41301ae78a vfs: Fix a regression in mounting proc
Gao feng <gaofeng@cn.fujitsu.com> reported that commit
e51db73532
userns: Better restrictions on when proc and sysfs can be mounted
caused a regression on mounting a new instance of proc in a mount
namespace created with user namespace privileges, when binfmt_misc
is mounted on /proc/sys/fs/binfmt_misc.

This is an unintended regression caused by the absolutely bogus empty
directory check in fs_fully_visible.  The check fs_fully_visible replaced
didn't even bother to attempt to verify proc was fully visible and
hiding proc files with any kind of mount is rare.  So for now fix
the userspace regression by allowing directory with nlink == 1
as /proc/sys/fs/binfmt_misc has.

I will have a better patch but it is not stable material, or
last minute kernel material.  So it will have to wait.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Gao feng <gaofeng@cn.fujitsu.com>
Tested-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-11-26 20:54:52 -08:00
Al Viro
48a066e72d RCU'd vfsmounts
* RCU-delayed freeing of vfsmounts
* vfsmount_lock replaced with a seqlock (mount_lock)
* sequence number from mount_lock is stored in nameidata->m_seq and
used when we exit RCU mode
* new vfsmount flag - MNT_SYNC_UMOUNT.  Set by umount_tree() when its
caller knows that vfsmount will have no surviving references.
* synchronize_rcu() done between unlocking namespace_sem in namespace_unlock()
and doing pending mntput().
* new helper: legitimize_mnt(mnt, seq).  Checks the mount_lock sequence
number against seq, then grabs reference to mnt.  Then it rechecks mount_lock
again to close the race and either returns success or drops the reference it
has acquired.  The subtle point is that in case of MNT_SYNC_UMOUNT we can
simply decrement the refcount and sod off - aforementioned synchronize_rcu()
makes sure that final mntput() won't come until we leave RCU mode.  We need
that, since we don't want to end up with some lazy pathwalk racing with
umount() and stealing the final mntput() from it - caller of umount() may
expect it to return only once the fs is shut down and we don't want to break
that.  In other cases (i.e. with MNT_SYNC_UMOUNT absent) we have to do
full-blown mntput() in case of mount_lock sequence number mismatch happening
just as we'd grabbed the reference, but in those cases we won't be stealing
the final mntput() from anything that would care.
* mntput_no_expire() doesn't lock anything on the fast path now.  Incidentally,
SMP and UP cases are handled the same way - no ifdefs there.
* normal pathname resolution does *not* do any writes to mount_lock.  It does,
of course, bump the refcounts of vfsmount and dentry in the very end, but that's
it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-11-09 00:16:19 -05:00
Al Viro
474279dc0f split __lookup_mnt() in two functions
Instead of passing the direction as argument (and checking it on every
step through the hash chain), just have separate __lookup_mnt() and
__lookup_mnt_last().  And use the standard iterators...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:35:00 -04:00
Al Viro
719ea2fbb5 new helpers: lock_mount_hash/unlock_mount_hash
aka br_write_{lock,unlock} of vfsmount_lock.  Inlines in fs/mount.h,
vfsmount_lock extern moved over there as well.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:59 -04:00
Al Viro
aba809cf09 namespace.c: get rid of mnt_ghosts
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:58 -04:00
Al Viro
9559f68915 fold dup_mnt_ns() into its only surviving caller
should've been done 6 years ago...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:58 -04:00
Al Viro
f6b742d869 mnt_set_expiry() doesn't need vfsmount_lock
->mnt_expire is protected by namespace_sem

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:57 -04:00
Al Viro
22a7919299 finish_automount() doesn't need vfsmount_lock for removal from expiry list
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:57 -04:00
Al Viro
085e83ff0c fs/namespace.c: bury long-dead define
MNT_WRITER_UNDERFLOW_LIMIT has been missed 4 years ago when it became unused.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:57 -04:00
Al Viro
649a795aff fold mntfree() into mntput_no_expire()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:56 -04:00
Al Viro
6339dab869 do_remount(): pull touch_mnt_namespace() up
... and don't bother with dropping and regaining vfsmount_lock

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:56 -04:00
Al Viro
aa7a574d0c dup_mnt_ns(): get rid of pointless grabbing of vfsmount_lock
mnt_list is protected by namespace_sem, not vfsmount_lock

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:55 -04:00
Al Viro
44bb4385ce fs_is_visible only needs namespace_sem held shared
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:55 -04:00
Al Viro
59aa0da8e2 initialize namespace_sem statically
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:54 -04:00
Al Viro
7b00ed6fe6 put_mnt_ns(): use drop_collected_mounts()
... rather than open-coding it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-10-24 23:34:52 -04:00
Rob Landley
57f150a58c initmpfs: move rootfs code from fs/ramfs/ to init/
When the rootfs code was a wrapper around ramfs, having them in the same
file made sense.  Now that it can wrap another filesystem type, move it in
with the init code instead.

This also allows a subsequent patch to access rootfstype= command line
arg.

Signed-off-by: Rob Landley <rob@landley.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jim Cromie <jim.cromie@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-11 15:59:37 -07:00
Al Viro
197df04c74 rename user_path_umountat() to user_path_mountpoint_at()
... and move the extern from linux/namei.h to fs/internal.h,
along with that of vfs_path_lookup().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-09-08 20:20:21 -04:00
Linus Torvalds
dc0755cdb1 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs pile 2 (of many) from Al Viro:
 "Mostly Miklos' series this time"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  constify dcache.c inlined helpers where possible
  fuse: drop dentry on failed revalidate
  fuse: clean up return in fuse_dentry_revalidate()
  fuse: use d_materialise_unique()
  sysfs: use check_submounts_and_drop()
  nfs: use check_submounts_and_drop()
  gfs2: use check_submounts_and_drop()
  afs: use check_submounts_and_drop()
  vfs: check unlinked ancestors before mount
  vfs: check submounts and drop atomically
  vfs: add d_walk()
  vfs: restructure d_genocide()
2013-09-07 14:36:57 -07:00
Linus Torvalds
c7c4591db6 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace changes from Eric Biederman:
 "This is an assorted mishmash of small cleanups, enhancements and bug
  fixes.

  The major theme is user namespace mount restrictions.  nsown_capable
  is killed as it encourages not thinking about details that need to be
  considered.  A very hard to hit pid namespace exiting bug was finally
  tracked and fixed.  A couple of cleanups to the basic namespace
  infrastructure.

  Finally there is an enhancement that makes per user namespace
  capabilities usable as capabilities, and an enhancement that allows
  the per userns root to nice other processes in the user namespace"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  userns:  Kill nsown_capable it makes the wrong thing easy
  capabilities: allow nice if we are privileged
  pidns: Don't have unshare(CLONE_NEWPID) imply CLONE_THREAD
  userns: Allow PR_CAPBSET_DROP in a user namespace.
  namespaces: Simplify copy_namespaces so it is clear what is going on.
  pidns: Fix hang in zap_pid_ns_processes by sending a potentially extra wakeup
  sysfs: Restrict mounting sysfs
  userns: Better restrictions on when proc and sysfs can be mounted
  vfs: Don't copy mount bind mounts of /proc/<pid>/ns/mnt between namespaces
  kernel/nsproxy.c: Improving a snippet of code.
  proc: Restrict mounting the proc filesystem
  vfs: Lock in place mounts from more privileged users
2013-09-07 14:35:32 -07:00
Miklos Szeredi
eed8100766 vfs: check unlinked ancestors before mount
We check submounts before doing d_drop() on a non-empty directory dentry in
NFS (have_submounts()), but we do not exclude a racing mount.  Nor do we
prevent mounts to be added to the disconnected subtree using relative paths
after the d_drop().

This patch fixes these issues by checking for unlinked (unhashed, non-root)
ancestors before proceeding with the mount.  This is done with rename
seqlock taken for write and with ->d_lock grabbed on each ancestor in turn,
including our dentry itself.  This ensures that the only one of
check_submounts_and_drop() or has_unlinked_ancestor() can succeed.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-09-05 16:23:50 -04:00
Jeff Layton
8033426e6b vfs: allow umount to handle mountpoints without revalidating them
Christopher reported a regression where he was unable to unmount a NFS
filesystem where the root had gone stale. The problem is that
d_revalidate handles the root of the filesystem differently from other
dentries, but d_weak_revalidate does not. We could simply fix this by
making d_weak_revalidate return success on IS_ROOT dentries, but there
are cases where we do want to revalidate the root of the fs.

A umount is really a special case. We generally aren't interested in
anything but the dentry and vfsmount that's attached at that point. If
the inode turns out to be stale we just don't care since the intent is
to stop using it anyway.

Try to handle this situation better by treating umount as a special
case in the lookup code. Have it resolve the parent using normal
means, and then do a lookup of the final dentry without revalidating
it. In most cases, the final lookup will come out of the dcache, but
the case where there's a trailing symlink or !LAST_NORM entry on the
end complicates things a bit.

Cc: Neil Brown <neilb@suse.de>
Reported-by: Christopher T Vogan <cvogan@us.ibm.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-09-03 22:50:29 -04:00
Eric W. Biederman
c7b96acf14 userns: Kill nsown_capable it makes the wrong thing easy
nsown_capable is a special case of ns_capable essentially for just CAP_SETUID and
CAP_SETGID.  For the existing users it doesn't noticably simplify things and
from the suggested patches I have seen it encourages people to do the wrong
thing.  So remove nsown_capable.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-08-30 23:44:11 -07:00
Eric W. Biederman
e51db73532 userns: Better restrictions on when proc and sysfs can be mounted
Rely on the fact that another flavor of the filesystem is already
mounted and do not rely on state in the user namespace.

Verify that the mounted filesystem is not covered in any significant
way.  I would love to verify that the previously mounted filesystem
has no mounts on top but there are at least the directories
/proc/sys/fs/binfmt_misc and /sys/fs/cgroup/ that exist explicitly
for other filesystems to mount on top of.

Refactor the test into a function named fs_fully_visible and call that
function from the mount routines of proc and sysfs.  This makes this
test local to the filesystems involved and the results current of when
the mounts take place, removing a weird threading of the user
namespace, the mount namespace and the filesystems themselves.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-08-26 19:17:03 -07:00
Eric W. Biederman
4ce5d2b1a8 vfs: Don't copy mount bind mounts of /proc/<pid>/ns/mnt between namespaces
Don't copy bind mounts of /proc/<pid>/ns/mnt between namespaces.
These files hold references to a mount namespace and copying them
between namespaces could result in a reference counting loop.

The current mnt_ns_loop test prevents loops on the assumption that
mounts don't cross between namespaces.  Unfortunately unsharing a
mount namespace and shared substrees can both cause mounts to
propogate between mount namespaces.

Add two flags CL_COPY_UNBINDABLE and CL_COPY_MNT_NS_FILE are added to
control this behavior, and CL_COPY_ALL is redefined as both of them.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-08-26 18:42:15 -07:00
Dan Carpenter
52e220d357 VFS: collect_mounts() should return an ERR_PTR
This should actually be returning an ERR_PTR on error instead of NULL.
That was how it was designed and all the callers expect it.

[AV: actually, that's what "VFS: Make clone_mnt()/copy_tree()/collect_mounts()
return errors" missed - originally collect_mounts() was expected to return
NULL on failure]

Cc: <stable@vger.kernel.org> # 3.10+
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-24 12:10:29 -04:00
Eric W. Biederman
5ff9d8a65c vfs: Lock in place mounts from more privileged users
When creating a less privileged mount namespace or propogating mounts
from a more privileged to a less privileged mount namespace lock the
submounts so they may not be unmounted individually in the child mount
namespace revealing what is under them.

This enforces the reasonable expectation that it is not possible to
see under a mount point.  Most of the time mounts are on empty
directories and revealing that does not matter, however I have seen an
occassionaly sloppy configuration where there were interesting things
concealed under a mount point that probably should not be revealed.

Expirable submounts are not locked because they will eventually
unmount automatically so whatever is under them already needs
to be safe for unprivileged users to access.

From a practical standpoint these restrictions do not appear to be
significant for unprivileged users of the mount namespace.  Recursive
bind mounts and pivot_root continues to work, and mounts that are
created in a mount namespace may be unmounted there.  All of which
means that the common idiom of keeping a directory of interesting
files and using pivot_root to throw everything else away continues to
work just fine.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-07-24 09:14:46 -07:00
Al Viro
b1983cd897 create_mnt_ns: unidiomatic use of list_add()
while list_add(A, B) and list_add(B, A) are equivalent when both A and B
are guaranteed to be empty, the usual idiom is list_add(what, where),
not the other way round...  Not a bug per se, but only by accident and
it makes RTFS harder for no good reason.

Spotted-by: Rajat Sharma <fs.rajat@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-05-04 15:18:53 -04:00
Al Viro
0d5cadb87e do_mount(): fix a leak introduced in 3.9 ("mount: consolidate permission checks")
Cc: stable@vger.kernel.org
Bisected-by: Michael Leun <lkml20130126@newton.leun.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-05-04 14:40:51 -04:00
Linus Torvalds
20b4fb4852 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull VFS updates from Al Viro,

Misc cleanups all over the place, mainly wrt /proc interfaces (switch
create_proc_entry to proc_create(), get rid of the deprecated
create_proc_read_entry() in favor of using proc_create_data() and
seq_file etc).

7kloc removed.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (204 commits)
  don't bother with deferred freeing of fdtables
  proc: Move non-public stuff from linux/proc_fs.h to fs/proc/internal.h
  proc: Make the PROC_I() and PDE() macros internal to procfs
  proc: Supply a function to remove a proc entry by PDE
  take cgroup_open() and cpuset_open() to fs/proc/base.c
  ppc: Clean up scanlog
  ppc: Clean up rtas_flash driver somewhat
  hostap: proc: Use remove_proc_subtree()
  drm: proc: Use remove_proc_subtree()
  drm: proc: Use minor->index to label things, not PDE->name
  drm: Constify drm_proc_list[]
  zoran: Don't print proc_dir_entry data in debug
  reiserfs: Don't access the proc_dir_entry in r_open(), r_start() r_show()
  proc: Supply an accessor for getting the data from a PDE's parent
  airo: Use remove_proc_subtree()
  rtl8192u: Don't need to save device proc dir PDE
  rtl8187se: Use a dir under /proc/net/r8180/
  proc: Add proc_mkdir_data()
  proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h}
  proc: Move PDE_NET() to fs/proc/proc_net.c
  ...
2013-05-01 17:51:54 -07:00
David Howells
0bb80f2405 proc: Split the namespace stuff out into linux/proc_ns.h
Split the proc namespace stuff out into linux/proc_ns.h.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: netdev@vger.kernel.org
cc: Serge E. Hallyn <serge.hallyn@ubuntu.com>
cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-05-01 17:29:39 -04:00
Linus Torvalds
e8f2b548de Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs fixes from Al Viro:
 "A nasty bug in fs/namespace.c caught by Andrey + a couple of less
  serious unpleasantness - ecryptfs misc device playing hopeless games
  with try_module_get() and palinfo procfs support being...  not quite
  correctly done, to be polite."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  mnt: release locks on error path in do_loopback
  palinfo fixes
  procfs: add proc_remove_subtree()
  ecryptfs: close rmmod race
2013-04-09 12:22:49 -07:00
Al Viro
97216be09e fold release_mounts() into namespace_unlock()
... and provide namespace_lock() as a trivial wrapper;
switch to those two consistently.

Result is patterned after rtnl_lock/rtnl_unlock pair.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:12:54 -04:00
Al Viro
328e6d9014 switch unlock_mount() to namespace_unlock(), convert all umount_tree() callers
which allows to kill the last argument of umount_tree() and make release_mounts()
static.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:12:53 -04:00
Al Viro
3ab6abee59 more conversions to namespace_unlock()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:12:53 -04:00
Al Viro
b54b9be782 get rid of the second argument of shrink_submounts()
... it's always &unmounted.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:12:53 -04:00
Al Viro
e3197d83d6 saner umount_tree()/release_mounts(), part 1
global list of release_mounts() fodder, protected by namespace_sem;
eventually, all umount_tree() callers will use it as kill list.
Helper picking the contents of that list, releasing namespace_sem
and doing release_mounts() on what it got.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:12:52 -04:00
Al Viro
84d17192d2 get rid of full-hash scan on detaching vfsmounts
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:12:52 -04:00
Andrey Vagin
e9c5d8a562 mnt: release locks on error path in do_loopback
do_loopback calls lock_mount(path) and forget to unlock_mount
if clone_mnt or copy_mnt fails.

[   77.661566] ================================================
[   77.662939] [ BUG: lock held when returning to user space! ]
[   77.664104] 3.9.0-rc5+ #17 Not tainted
[   77.664982] ------------------------------------------------
[   77.666488] mount/514 is leaving the kernel with locks still held!
[   77.668027] 2 locks held by mount/514:
[   77.668817]  #0:  (&sb->s_type->i_mutex_key#7){+.+.+.}, at: [<ffffffff811cca22>] lock_mount+0x32/0xe0
[   77.671755]  #1:  (&namespace_sem){+++++.}, at: [<ffffffff811cca3a>] lock_mount+0x4a/0xe0

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-04-09 14:09:50 -04:00
Eric W. Biederman
87a8ebd637 userns: Restrict when proc and sysfs can be mounted
Only allow unprivileged mounts of proc and sysfs if they are already
mounted when the user namespace is created.

proc and sysfs are interesting because they have content that is
per namespace, and so fresh mounts are needed when new namespaces
are created while at the same time proc and sysfs have content that
is shared between every instance.

Respect the policy of who may see the shared content of proc and sysfs
by only allowing new mounts if there was an existing mount at the time
the user namespace was created.

In practice there are only two interesting cases: proc and sysfs are
mounted at their usual places, proc and sysfs are not mounted at all
(some form of mount namespace jail).

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-27 07:50:08 -07:00
Eric W. Biederman
132c94e31b vfs: Carefully propogate mounts across user namespaces
As a matter of policy MNT_READONLY should not be changable if the
original mounter had more privileges than creator of the mount
namespace.

Add the flag CL_UNPRIVILEGED to note when we are copying a mount from
a mount namespace that requires more privileges to a mount namespace
that requires fewer privileges.

When the CL_UNPRIVILEGED flag is set cause clone_mnt to set MNT_NO_REMOUNT
if any of the mnt flags that should never be changed are set.

This protects both mount propagation and the initial creation of a less
privileged mount namespace.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-27 07:50:05 -07:00
Eric W. Biederman
90563b198e vfs: Add a mount flag to lock read only bind mounts
When a read-only bind mount is copied from mount namespace in a higher
privileged user namespace to a mount namespace in a lesser privileged
user namespace, it should not be possible to remove the the read-only
restriction.

Add a MNT_LOCK_READONLY mount flag to indicate that a mount must
remain read-only.

CC: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-27 07:50:04 -07:00
Eric W. Biederman
3151527ee0 userns: Don't allow creation if the user is chrooted
Guarantee that the policy of which files may be access that is
established by setting the root directory will not be violated
by user namespaces by verifying that the root directory points
to the root of the mount namespace at the time of user namespace
creation.

Changing the root is a privileged operation, and as a matter of policy
it serves to limit unprivileged processes to files below the current
root directory.

For reasons of simplicity and comprehensibility the privilege to
change the root directory is gated solely on the CAP_SYS_CHROOT
capability in the user namespace.  Therefore when creating a user
namespace we must ensure that the policy of which files may be access
can not be violated by changing the root directory.

Anyone who runs a processes in a chroot and would like to use user
namespace can setup the same view of filesystems with a mount
namespace instead.  With this result that this is not a practical
limitation for using user namespaces.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-27 07:49:29 -07:00
Al Viro
496ad9aa8e new helper: file_inode(file)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-02-22 23:31:31 -05:00
Al Viro
57eccb830f mount: consolidate permission checks
... and ask for global CAP_SYS_ADMIN only for superblock-level remounts

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-02-22 23:31:31 -05:00
Al Viro
9b40bc90ab get rid of unprotected dereferencing of mnt->mnt_ns
It's safe only under namespace_sem or vfsmount_lock; all places
in fs/namespace.c that want mnt->mnt_ns->user_ns actually want to use
current->nsproxy->mnt_ns->user_ns (note the calls of check_mnt() in
there).

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-02-22 23:31:05 -05:00
Miao Xie
1e75529e3c vfs, freeze: use ACCESS_ONCE() to guard access to ->mnt_flags
The compiler may optimize the while loop and make the check just be done once,
so we should use ACCESS_ONCE() to guard access to ->mnt_flags

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-12-20 13:36:18 -05:00
Eric W. Biederman
5e4a08476b userns: Require CAP_SYS_ADMIN for most uses of setns.
Andy Lutomirski <luto@amacapital.net> found a nasty little bug in
the permissions of setns.  With unprivileged user namespaces it
became possible to create new namespaces without privilege.

However the setns calls were relaxed to only require CAP_SYS_ADMIN in
the user nameapce of the targed namespace.

Which made the following nasty sequence possible.

pid = clone(CLONE_NEWUSER | CLONE_NEWNS);
if (pid == 0) { /* child */
	system("mount --bind /home/me/passwd /etc/passwd");
}
else if (pid != 0) { /* parent */
	char path[PATH_MAX];
	snprintf(path, sizeof(path), "/proc/%u/ns/mnt");
	fd = open(path, O_RDONLY);
	setns(fd, 0);
	system("su -");
}

Prevent this possibility by requiring CAP_SYS_ADMIN
in the current user namespace when joing all but the user namespace.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2012-12-14 16:12:03 -08:00
Eric W. Biederman
98f842e675 proc: Usable inode numbers for the namespace file descriptors.
Assign a unique proc inode to each namespace, and use that
inode number to ensure we only allocate at most one proc
inode for every namespace in proc.

A single proc inode per namespace allows userspace to test
to see if two processes are in the same namespace.

This has been a long requested feature and only blocked because
a naive implementation would put the id in a global space and
would ultimately require having a namespace for the names of
namespaces, making migration and certain virtualization tricks
impossible.

We still don't have per superblock inode numbers for proc, which
appears necessary for application unaware checkpoint/restart and
migrations (if the application is using namespace file descriptors)
but that is now allowd by the design if it becomes important.

I have preallocated the ipc and uts initial proc inode numbers so
their structures can be statically initialized.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-11-20 04:19:49 -08:00
Zhao Hongjiang
ae11e0f184 userns: fix return value on mntns_install() failure
Change return value from -EINVAL to -EPERM when the permission check fails.

Signed-off-by: Zhao Hongjiang <zhaohongjiang@huawei.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-11-19 05:59:22 -08:00
Eric W. Biederman
0c55cfc416 vfs: Allow unprivileged manipulation of the mount namespace.
- Add a filesystem flag to mark filesystems that are safe to mount as
  an unprivileged user.

- Add a filesystem flag to mark filesystems that don't need MNT_NODEV
  when mounted by an unprivileged user.

- Relax the permission checks to allow unprivileged users that have
  CAP_SYS_ADMIN permissions in the user namespace referred to by the
  current mount namespace to be allowed to mount, unmount, and move
  filesystems.

Acked-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2012-11-19 05:59:21 -08:00
Eric W. Biederman
7a472ef4be vfs: Only support slave subtrees across different user namespaces
Sharing mount subtress with mount namespaces created by unprivileged
users allows unprivileged mounts created by unprivileged users to
propagate to mount namespaces controlled by privileged users.

Prevent nasty consequences by changing shared subtrees to slave
subtress when an unprivileged users creates a new mount namespace.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2012-11-19 05:59:20 -08:00
Eric W. Biederman
771b137168 vfs: Add a user namespace reference from struct mnt_namespace
This will allow for support for unprivileged mounts in a new user namespace.

Acked-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2012-11-19 05:59:19 -08:00
Eric W. Biederman
8823c079ba vfs: Add setns support for the mount namespace
setns support for the mount namespace is a little tricky as an
arbitrary decision must be made about what to set fs->root and
fs->pwd to, as there is no expectation of a relationship between
the two mount namespaces.  Therefore I arbitrarily find the root
mount point, and follow every mount on top of it to find the top
of the mount stack.  Then I set fs->root and fs->pwd to that
location.  The topmost root of the mount stack seems like a
reasonable place to be.

Bind mount support for the mount namespace inodes has the
possibility of creating circular dependencies between mount
namespaces.  Circular dependencies can result in loops that
prevent mount namespaces from every being freed.  I avoid
creating those circular dependencies by adding a sequence number
to the mount namespace and require all bind mounts be of a
younger mount namespace into an older mount namespace.

Add a helper function proc_ns_inode so it is possible to
detect when we are attempting to bind mound a namespace inode.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-11-19 05:59:18 -08:00
Jeff Layton
91a27b2a75 vfs: define struct filename and have getname() return it
getname() is intended to copy pathname strings from userspace into a
kernel buffer. The result is just a string in kernel space. It would
however be quite helpful to be able to attach some ancillary info to
the string.

For instance, we could attach some audit-related info to reduce the
amount of audit-related processing needed. When auditing is enabled,
we could also call getname() on the string more than once and not
need to recopy it from userspace.

This patchset converts the getname()/putname() interfaces to return
a struct instead of a string. For now, the struct just tracks the
string in kernel space and the original userland pointer for it.

Later, we'll add other information to the struct as it becomes
convenient.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-10-12 20:14:55 -04:00
Al Viro
808d4e3cfd consitify do_mount() arguments
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-10-11 20:02:04 -04:00
Al Viro
156cacb1d0 do_add_mount()/umount -l races
normally we deal with lock_mount()/umount races by checking that
mountpoint to be is still in our namespace after lock_mount() has
been done.  However, do_add_mount() skips that check when called
with MNT_SHRINKABLE in flags (i.e. from finish_automount()).  The
reason is that ->mnt_ns may be a temporary namespace created exactly
to contain automounts a-la NFS4 referral handling.  It's not the
namespace of the caller, though, so check_mnt() would fail here.
We still need to check that ->mnt_ns is non-NULL in that case,
though.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-09-22 20:48:18 -04:00
Jan Kara
eb04c28288 fs: Add freezing handling to mnt_want_write() / mnt_drop_write()
Most of places where we want freeze protection coincides with the places where
we also have remount-ro protection. So make mnt_want_write() and
mnt_drop_write() (and their _file alternative) prevent freezing as well.
For the few cases that are really interested only in remount-ro protection
provide new function variants.

BugLink: https://bugs.launchpad.net/bugs/897421
Tested-by: Kamal Mostafa <kamal@canonical.com>
Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com>
Tested-by: Dann Frazier <dann.frazier@canonical.com>
Tested-by: Massimo Morana <massimo.morana@canonical.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-31 09:40:38 +04:00
David Howells
f015f1267b VFS: Comment mount following code
Add comments describing what the directions "up" and "down" mean and ref count
handling to the VFS mount following family of functions.

Signed-off-by: Valerie Aurora <vaurora@redhat.com> (Original author)
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-14 16:38:32 +04:00
David Howells
be34d1a3bc VFS: Make clone_mnt()/copy_tree()/collect_mounts() return errors
copy_tree() can theoretically fail in a case other than ENOMEM, but always
returns NULL which is interpreted by callers as -ENOMEM.  Change it to return
an explicit error.

Also change clone_mnt() for consistency and because union mounts will add new
error cases.

Thanks to Andreas Gruenbacher <agruen@suse.de> for a bug fix.
[AV: folded braino fix by Dan Carpenter]

Original-author: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Valerie Aurora <valerie.aurora@gmail.com>
Cc: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-14 16:37:27 +04:00
Al Viro
6ce6e24e72 get rid of magic in proc_namespace.c
don't rely on proc_mounts->m being the first field; container_of()
is there for purpose.  No need to bother with ->private, while
we are at it - the same container_of will do nicely.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-14 16:32:48 +04:00
Al Viro
f7a99c5b7c get rid of ->mnt_longterm
it's enough to set ->mnt_ns of internal vfsmounts to something
distinct from all struct mnt_namespace out there; then we can
just use the check for ->mnt_ns != NULL in the fast path of
mntput_no_expire()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-07-14 16:32:47 +04:00