[34-longterm 093/247] ocfs2_connection_find() returns pointer to bad structure

[Paul Gortmaker]

From: dann frazier <dann.frazier@xxxxxxxxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 226291aa4641fa13cb5dec3bcb3379faa83009e2 upstream.

If ocfs2_live_connection_list is empty, ocfs2_connection_find() will return
a pointer to the LIST_HEAD, cast as a ocfs2_live_connection. This can cause
an oops when ocfs2_control_send_down() dereferences c->oc_conn:

Call Trace:
  [<ffffffffa00c2a3c>] ocfs2_control_message+0x28c/0x2b0 [ocfs2_stack_user]
  [<ffffffffa00c2a95>] ocfs2_control_write+0x35/0xb0 [ocfs2_stack_user]
  [<ffffffff81143a88>] vfs_write+0xb8/0x1a0
  [<ffffffff8155cc13>] ? do_page_fault+0x153/0x3b0
  [<ffffffff811442f1>] sys_write+0x51/0x80
  [<ffffffff810121b2>] system_call_fastpath+0x16/0x1b

Fix by explicitly returning NULL if no match is found.

Signed-off-by: dann frazier <dann.frazier@xxxxxxxxxxxxx>
Signed-off-by: Joel Becker <joel.becker@xxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 fs/ocfs2/stack_user.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/ocfs2/stack_user.c b/fs/ocfs2/stack_user.c
index 2dc57bc..22db114 100644
--- a/fs/ocfs2/stack_user.c
+++ b/fs/ocfs2/stack_user.c
@@ -191,7 +191,7 @@ static struct ocfs2_live_connection *ocfs2_connection_find(const char *name)
 			return c;
 	}
 
-	return c;
+	return NULL;
 }
 
 /*
-- 
1.7.4.4

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