[ 166/171] libceph: avoid NULL kref_put when osd reset races with alloc_msg

[Greg Kroah-Hartman]

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

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

From: Sage Weil <sage@xxxxxxxxxxx>

(cherry picked from commit 9bd952615a42d7e2ce3fa2c632e808e804637a1a)

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@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ceph/messenger.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2746,7 +2746,8 @@ 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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