From: Eric W. Biederman <ebiederm@xmission.com>
Date: Mon, 19 Jan 2015 17:48:45 +0000 (-0600)
Subject: mnt: Fix the error check in __detach_mounts
X-Git-Tag: v3.18.17~15
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5d4bafa7be0843b63b6368ae49aaf0f5a941fc9f;p=thirdparty%2Fkernel%2Fstable.git

mnt: Fix the error check in __detach_mounts

[ Upstream commit f53e57975151f54ad8caa1b0ac8a78091cd5700a ]

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: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 8b60287a488bc..a19d05c4ebe5f 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1490,7 +1490,7 @@ void __detach_mounts(struct dentry *dentry)
 
 	namespace_lock();
 	mp = lookup_mountpoint(dentry);
-	if (!mp)
+	if (IS_ERR_OR_NULL(mp))
 		goto out_unlock;
 
 	lock_mount_hash();