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-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f53e57975151f54ad8caa1b0ac8a78091cd5700a;p=linux-beck.git

mnt: Fix the error check in __detach_mounts

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>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 1894d1878dbc..e8f7f8c58c3c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1516,7 +1516,7 @@ 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();