[3.13.y.z extended stable] Patch "posix_acl: handle NULL ACL in posix_acl_equiv_mode" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    posix_acl: handle NULL ACL in posix_acl_equiv_mode

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6fff215de29a28d8af0838d0d1a2f82ff68af121 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch at lst.de>
Date: Sun, 4 May 2014 13:03:32 +0200
Subject: posix_acl: handle NULL ACL in posix_acl_equiv_mode

commit 50c6e282bdf5e8dabf8d7cf7b162545a55645fd9 upstream.

Various filesystems don't bother checking for a NULL ACL in
posix_acl_equiv_mode, and thus can dereference a NULL pointer when it
gets passed one. This usually happens from the NFS server, as the ACL tools
never pass a NULL ACL, but instead of one representing the mode bits.

Instead of adding boilerplat to all filesystems put this check into one place,
which will allow us to remove the check from other filesystems as well later
on.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Reported-by: Ben Greear <greearb at candelatech.com>
Reported-by: Marco Munderloh <munderl at tnt.uni-hannover.de>,
Cc: Chuck Lever <chuck.lever at oracle.com>
Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/posix_acl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 8bd2135..3542f1f 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -158,6 +158,12 @@ posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 	umode_t mode = 0;
 	int not_equiv = 0;

+	/*
+	 * A null ACL can always be presented as mode bits.
+	 */
+	if (!acl)
+		return 0;
+
 	FOREACH_ACL_ENTRY(pa, acl, pe) {
 		switch (pa->e_tag) {
 			case ACL_USER_OBJ:
--
1.9.1