[PATCH 3.14 53/77] ceph: fix null pointer dereference in discard_cap_releases()

Greg Kroah-Hartman
2015-01-14T07:35:48Z

From: "Yan, Zheng" <zheng.z.yan@intel.com>

commit 00bd8edb861eb41d274938cfc0338999d9c593a3 upstream.

send_mds_reconnect() may call discard_cap_releases() after all
release messages have been dropped by cleanup_cap_releases()

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Cc: Markus Blank-Burian <burian@muenster.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ceph/mds_client.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1461,15 +1461,18 @@ static void discard_cap_releases(struct

dout("discard_cap_releases mds%d\n", session->s_mds);

- /* zero out the in-progress message */
- msg = list_first_entry(&session->s_cap_releases,
- struct ceph_msg, list_head);
- head = msg->front.iov_base;
- num = le32_to_cpu(head->num);
- dout("discard_cap_releases mds%d %p %u\n", session->s_mds, msg, num);
- head->num = cpu_to_le32(0);
- msg->front.iov_len = sizeof(*head);
- session->s_num_cap_releases += num;
+ if (!list_empty(&session->s_cap_releases)) {
+ /* zero out the in-progress message */
+ msg = list_first_entry(&session->s_cap_releases,
+ struct ceph_msg, list_head);
+ head = msg->front.iov_base;
+ num = le32_to_cpu(head->num);
+ dout("discard_cap_releases mds%d %p %u\n",
+ session->s_mds, msg, num);
+ head->num = cpu_to_le32(0);
+ msg->front.iov_len = sizeof(*head);
+ session->s_num_cap_releases += num;
+ }

/* requeue completed messages */
while (!list_empty(&session->s_cap_releases_done)) {