3.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sage Weil <s...@inktank.com>

commit 9bd952615a42d7e2ce3fa2c632e808e804637a1a upstream.

The ceph_on_in_msg_alloc() method drops con->mutex while it allocates a
message.  If that races with a timeout that resends a zillion messages and
resets the connection, and the ->alloc_msg() method returns a NULL message,
it will call ceph_msg_put(NULL) and BUG.

Fix by only calling put if msg is non-NULL.

Fixes http://tracker.newdream.net/issues/3142

Signed-off-by: Sage Weil <s...@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 net/ceph/messenger.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2750,7 +2750,8 @@ static int ceph_con_in_msg_alloc(struct
                msg = con->ops->alloc_msg(con, hdr, skip);
                mutex_lock(&con->mutex);
                if (con->state != CON_STATE_OPEN) {
-                       ceph_msg_put(msg);
+                       if (msg)
+                               ceph_msg_put(msg);
                        return -EAGAIN;
                }
                con->in_msg = msg;


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