linux-stable.git/fs/namespace.c, branch v4.0.2

mnt: Update detach_mounts to leave mounts connected

2015-05-06T20:03:51+00:00

commit e0c9c0afd2fc958ffa34b697972721d81df8a56f upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Fix the error check in __detach_mounts

2015-05-06T20:03:51+00:00

commit f53e57975151f54ad8caa1b0ac8a78091cd5700a upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Honor MNT_LOCKED when detaching mounts

2015-05-06T20:03:51+00:00

commit ce07d891a0891d3c0d0c2d73d577490486b809e1 upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Factor umount_mnt from umount_tree

2015-05-06T20:03:51+00:00

commit 6a46c5735c29175da55b2fa9d53775182422cdd7 upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Factor out unhash_mnt from detach_mnt and umount_tree

2015-05-06T20:03:51+00:00

commit 7bdb11de8ee4f4ae195e2fa19efd304e0b36c63b upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: On an unmount propagate clearing of MNT_LOCKED

2015-05-06T20:03:51+00:00

commit 5d88457eb5b86b475422dc882f089203faaeedb5 upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Delay removal from the mount hash.

2015-05-06T20:03:51+00:00

commit 411a938b5abc9cb126c41cccf5975ae464fe0f3e upstream.

- 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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Add MNT_UMOUNT flag

2015-05-06T20:03:50+00:00

commit 590ce4bcbfb4e0462a720a4ad901e84416080bba upstream.

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

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: In umount_tree reuse mnt_list instead of mnt_hash

2015-05-06T20:03:50+00:00

commit c003b26ff98ca04a180ff34c38c007a3998d62f9 upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

mnt: Don't propagate umounts in __detach_mounts

2015-05-06T20:03:50+00:00

commit 8318e667f176f7ea34451a1a530634e293f216ac upstream.

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.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman