[PATCH 147/270] libceph: avoid NULL kref_put when osd reset races with alloc_msg

[Herton Ronaldo Krzesinski]

3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.

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

From: Sage Weil <sage at 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 <sage at inktank.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 net/ceph/messenger.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 0de041f..692243a 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2746,7 +2746,8 @@ static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip)
 		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;
-- 
1.7.9.5