From 92a34c870562539755aa2d8eb4b8d2b9cdc3bbe4 Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Mon, 24 Mar 2014 09:56:43 +0800 Subject: [PATCH] ceph: fix null pointer dereference in discard_cap_releases() 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 Reviewed-by: Sage Weil Cc: Markus Blank-Burian Signed-off-by: Greg Kroah-Hartman --- fs/ceph/mds_client.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index f4f050a..339c412 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -1461,15 +1461,18 @@ 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)) { -- 1.9.1