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  1. 09 Apr, 2015 7 commits
    • Eric W. Biederman's avatar
      mnt: Update detach_mounts to leave mounts connected · e0c9c0af
      Eric W. Biederman authored 
      Now that it is possible to lazily unmount an entire mount tree and
leave the individual mounts connected to each other add a new flag
UMOUNT_CONNECTED to umount_tree to force this behavior and use
this flag in detach_mounts.

This closes a bug where the deletion of a file or directory could
trigger an unmount and reveal data under a mount point.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      e0c9c0af
    • Eric W. Biederman's avatar
      mnt: Fix the error check in __detach_mounts · f53e5797
      Eric W. Biederman authored 
      lookup_mountpoint can return either NULL or an error value.
Update the test in __detach_mounts to test for an error value
to avoid pathological cases causing a NULL pointer dereferences.

The callers of __detach_mounts should prevent it from ever being
called on an unlinked dentry but don't take any chances.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      f53e5797
    • Eric W. Biederman's avatar
      mnt: Honor MNT_LOCKED when detaching mounts · ce07d891
      Eric W. Biederman authored 
      Modify umount(MNT_DETACH) to keep mounts in the hash table that are
locked to their parent mounts, when the parent is lazily unmounted.

In mntput_no_expire detach the children from the hash table, depending
on mnt_pin_kill in cleanup_mnt to decrement the mnt_count of the children.

In __detach_mounts if there are any mounts that have been unmounted
but still are on the list of mounts of a mountpoint, remove their
children from the mount hash table and those children to the unmounted
list so they won't linger potentially indefinitely waiting for their
final mntput, now that the mounts serve no purpose.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      ce07d891
    • Eric W. Biederman's avatar
      fs_pin: Allow for the possibility that m_list or s_list go unused. · 820f9f14
      Eric W. Biederman authored 
      This is needed to support lazily umounting locked mounts.  Because the
entire unmounted subtree needs to stay together until there are no
users with references to any part of the subtree.

To support this guarantee that the fs_pin m_list and s_list nodes
are initialized by initializing them in init_fs_pin allowing
for the possibility that pin_insert_group does not touch them.

Further use hlist_del_init in pin_remove so that there is
a hlist_unhashed test before the list we attempt to update
the previous list item.
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      820f9f14
    • Eric W. Biederman's avatar
      mnt: Factor umount_mnt from umount_tree · 6a46c573
      Eric W. Biederman authored 
      For future use factor out a function umount_mnt from umount_tree.
This function unhashes a mount and remembers where the mount
was mounted so that eventually when the code makes it to a
sleeping context the mountpoint can be dput.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      6a46c573
    • Eric W. Biederman's avatar
      mnt: Factor out unhash_mnt from detach_mnt and umount_tree · 7bdb11de
      Eric W. Biederman authored 
      Create a function unhash_mnt that contains the common code between
detach_mnt and umount_tree, and use unhash_mnt in place of the common
code.  This add a unncessary list_del_init(mnt->mnt_child) into
umount_tree but given that mnt_child is already empty this extra
line is a noop.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      7bdb11de
    • Eric W. Biederman's avatar
      mnt: Fail collect_mounts when applied to unmounted mounts · cd4a4017
      Eric W. Biederman authored 
      The only users of collect_mounts are in audit_tree.c

In audit_trim_trees and audit_add_tree_rule the path passed into
collect_mounts is generated from kern_path passed an audit_tree
pathname which is guaranteed to be an absolute path.   In those cases
collect_mounts is obviously intended to work on mounted paths and
if a race results in paths that are unmounted when collect_mounts
it is reasonable to fail early.

The paths passed into audit_tag_tree don't have the absolute path
check.  But are used to play with fsnotify and otherwise interact with
the audit_trees, so again operating only on mounted paths appears
reasonable.

Avoid having to worry about what happens when we try and audit
unmounted filesystems by restricting collect_mounts to mounts
that appear in the mount tree.
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      cd4a4017
  3. 03 Apr, 2015 8 commits
    • Eric W. Biederman's avatar
      mnt: Don't propagate unmounts to locked mounts · 0c56fe31
      Eric W. Biederman authored 
      If the first mount in shared subtree is locked don't unmount the
shared subtree.

This is ensured by walking through the mounts parents before children
and marking a mount as unmountable if it is not locked or it is locked
but it's parent is marked.

This allows recursive mount detach to propagate through a set of
mounts when unmounting them would not reveal what is under any locked
mount.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      0c56fe31
    • Eric W. Biederman's avatar
      mnt: On an unmount propagate clearing of MNT_LOCKED · 5d88457e
      Eric W. Biederman authored 
      A prerequisite of calling umount_tree is that the point where the tree
is mounted at is valid to unmount.

If we are propagating the effect of the unmount clear MNT_LOCKED in
every instance where the same filesystem is mounted on the same
mountpoint in the mount tree, as we know (by virtue of the fact
that umount_tree was called) that it is safe to reveal what
is at that mountpoint.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      5d88457e
    • Eric W. Biederman's avatar
      mnt: Delay removal from the mount hash. · 411a938b
      Eric W. Biederman authored 
      - Modify __lookup_mnt_hash_last to ignore mounts that have MNT_UMOUNTED set.
- Don't remove mounts from the mount hash table in propogate_umount
- Don't remove mounts from the mount hash table in umount_tree before
  the entire list of mounts to be umounted is selected.
- Remove mounts from the mount hash table as the last thing that
  happens in the case where a mount has a parent in umount_tree.
  Mounts without parents are not hashed (by definition).

This paves the way for delaying removal from the mount hash table even
farther and fixing the MNT_LOCKED vs MNT_DETACH issue.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      411a938b
    • Eric W. Biederman's avatar
      mnt: Add MNT_UMOUNT flag · 590ce4bc
      Eric W. Biederman authored 
      In some instances it is necessary to know if the the unmounting
process has begun on a mount.  Add MNT_UMOUNT to make that reliably
testable.

This fix gets used in fixing locked mounts in MNT_DETACH

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      590ce4bc
    • Eric W. Biederman's avatar
      mnt: In umount_tree reuse mnt_list instead of mnt_hash · c003b26f
      Eric W. Biederman authored 
      umount_tree builds a list of mounts that need to be unmounted.
Utilize mnt_list for this purpose instead of mnt_hash.  This begins to
allow keeping a mount on the mnt_hash after it is unmounted, which is
necessary for a properly functioning MNT_LOCKED implementation.

The fact that mnt_list is an ordinary list makding available list_move
is nice bonus.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      c003b26f
    • Eric W. Biederman's avatar
      mnt: Don't propagate umounts in __detach_mounts · 8318e667
      Eric W. Biederman authored 
      Invoking mount propagation from __detach_mounts is inefficient and
wrong.

It is inefficient because __detach_mounts already walks the list of
mounts that where something needs to be done, and mount propagation
walks some subset of those mounts again.

It is actively wrong because if the dentry that is passed to
__detach_mounts is not part of the path to a mount that mount should
not be affected.

change_mnt_propagation(p,MS_PRIVATE) modifies the mount propagation
tree of a master mount so it's slaves are connected to another master
if possible.  Which means even removing a mount from the middle of a
mount tree with __detach_mounts will not deprive any mount propagated
mount events.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      8318e667
    • Eric W. Biederman's avatar
      mnt: Improve the umount_tree flags · e819f152
      Eric W. Biederman authored 
      - Remove the unneeded declaration from pnode.h
- Mark umount_tree static as it has no callers outside of namespace.c
- Define an enumeration of umount_tree's flags.
- Pass umount_tree's flags in by name

This removes the magic numbers 0, 1 and 2 making the code a little
clearer and makes it possible for there to be lazy unmounts that don't
propagate.  Which is what __detach_mounts actually wants for example.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      e819f152
    • Eric W. Biederman's avatar
      mnt: Use hlist_move_list in namespace_unlock · a3b3c562
      Eric W. Biederman authored 
      Small cleanup to make the code more readable and maintainable.
Signed-off-by: default avatarEric Biederman <ebiederm@xmission.com>
      a3b3c562
  5. 29 Mar, 2015 7 commits
  7. 28 Mar, 2015 9 commits
  9. 27 Mar, 2015 6 commits
  11. 26 Mar, 2015 3 commits
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