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mnt: Clarify and correct the disconnect logic in umount_tree

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commit f2d0a123bc upstream.

rmdir mntpoint will result in an infinite loop when there is
a mount locked on the mountpoint in another mount namespace.

This is because the logic to test to see if a mount should
be disconnected in umount_tree is buggy.

Move the logic to decide if a mount should remain connected to
it's mountpoint into it's own function disconnect_mount so that
clarity of expression instead of terseness of expression becomes
a virtue.

When the conditions where it is invalid to leave a mount connected
are first ruled out, the logic for deciding if a mount should
be disconnected becomes much clearer and simpler.

Fixes: e0c9c0afd2 mnt: Update detach_mounts to leave mounts connected
Fixes: ce07d891a0 mnt: Honor MNT_LOCKED when detaching mounts
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric W. Biederman
2015-07-17 14:15:30 -05:00
committed by Greg Kroah-Hartman
parent 59366187ef
commit 4647b34f1a
2 changed files with 31 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
fs/namespace.c
View File

@@ -1350,6 +1350,36 @@ enum umount_tree_flags {
UMOUNT_PROPAGATE = 2, UMOUNT_PROPAGATE = 2,
UMOUNT_CONNECTED = 4, UMOUNT_CONNECTED = 4,
}; };
static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
{
/* Leaving mounts connected is only valid for lazy umounts */
if (how & UMOUNT_SYNC)
return true;
/* A mount without a parent has nothing to be connected to */
if (!mnt_has_parent(mnt))
return true;
/* Because the reference counting rules change when mounts are
* unmounted and connected, umounted mounts may not be
* connected to mounted mounts.
*/
if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
return true;
/* Has it been requested that the mount remain connected? */
if (how & UMOUNT_CONNECTED)
return false;
/* Is the mount locked such that it needs to remain connected? */
if (IS_MNT_LOCKED(mnt))
return false;
/* By default disconnect the mount */
return true;
}
/* /*
* mount_lock must be held * mount_lock must be held
* namespace_sem must be held for write * namespace_sem must be held for write
@@ -1387,10 +1417,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
if (how & UMOUNT_SYNC) if (how & UMOUNT_SYNC)
p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
disconnect = !(((how & UMOUNT_CONNECTED) && disconnect = disconnect_mount(p, how);
mnt_has_parent(p) &&
(p->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) ||
IS_MNT_LOCKED_AND_LAZY(p));
pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
disconnect ? &unmounted : NULL); disconnect ? &unmounted : NULL);

2
fs/pnode.h
View File

@@ -20,8 +20,6 @@
#define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED) #define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED)
#define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED) #define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED)
#define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED) #define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED)
#define IS_MNT_LOCKED_AND_LAZY(m) \
(((m)->mnt.mnt_flags & (MNT_LOCKED|MNT_SYNC_UMOUNT)) == MNT_LOCKED)
#define CL_EXPIRE 0x01 #define CL_EXPIRE 0x01
#define CL_SLAVE 0x02 #define CL_SLAVE 0x02