From: Yan, Zheng Date: Mon, 24 Mar 2014 01:56:43 +0000 (+0800) Subject: ceph: fix null pointer dereference in discard_cap_releases() X-Git-Tag: v3.15-rc1~61^2~47 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=00bd8edb861eb41d274938cfc0338999d9c593a3;p=linux.git ceph: fix null pointer dereference in discard_cap_releases() send_mds_reconnect() may call discard_cap_releases() after all release messages have been dropped by cleanup_cap_releases() Signed-off-by: Yan, Zheng Reviewed-by: Sage Weil --- diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index f260bd8d61cd..77640ada487a 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -1462,15 +1462,18 @@ static void discard_cap_releases(struct ceph_mds_client *mdsc, 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)) {