libceph: avoid NULL kref_put when osd reset races with alloc_msg

(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@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 84f34c3f3e900e0b3a81c36ad87b12c975a672af..aa71a67450afa4d41f32cfaed09776b5b5552c49 100644 (file)
--- 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;