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Commit 32224b87 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Greg Kroah-Hartman
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mount: Retest MNT_LOCKED in do_umount 



commit 25d202ed820ee347edec0bf3bf553544556bf64b upstream.

It was recently pointed out that the one instance of testing MNT_LOCKED
outside of the namespace_sem is in ksys_umount.

Fix that by adding a test inside of do_umount with namespace_sem and
the mount_lock held.  As it helps to fail fails the existing test is
maintained with an additional comment pointing out that it may be racy
because the locks are not held.

Cc: stable@vger.kernel.org
Reported-by: default avatarAl Viro <viro@ZenIV.linux.org.uk>
Fixes: 5ff9d8a6 ("vfs: Lock in place mounts from more privileged users")
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4d01f031

fs/namespace.c

+8 −2
Original line number Diff line number Diff line
@@ -1540,8 +1540,13 @@ static int do_umount(struct mount *mnt, int flags) 


	namespace_lock();

	lock_mount_hash();

	event++;



	/* Recheck MNT_LOCKED with the locks held */

	retval = -EINVAL;

	if (mnt->mnt.mnt_flags & MNT_LOCKED)

		goto out;



	event++;

	if (flags & MNT_DETACH) {

		if (!list_empty(&mnt->mnt_list))

			umount_tree(mnt, UMOUNT_PROPAGATE);
@@ -1555,6 +1560,7 @@ static int do_umount(struct mount *mnt, int flags) 
			retval = 0;

		}

	}

out:

	unlock_mount_hash();

	namespace_unlock();

	return retval;
@@ -1645,7 +1651,7 @@ int ksys_umount(char __user *name, int flags) 
		goto dput_and_out;

	if (!check_mnt(mnt))

		goto dput_and_out;

	if (mnt->mnt.mnt_flags & MNT_LOCKED)

	if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */

		goto dput_and_out;

	retval = -EPERM;

	if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))