From 05676fe53c9f26fe703c57b14bdd0807e23cc33b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 13 Aug 2015 15:44:51 -0700 Subject: [PATCH 1/2] inet: fix potential deadlock in reqsk_queue_unlink() When replacing del_timer() with del_timer_sync(), I introduced a deadlock condition : reqsk_queue_unlink() is called from inet_csk_reqsk_queue_drop() inet_csk_reqsk_queue_drop() can be called from many contexts, one being the timer handler itself (reqsk_timer_handler()). In this case, del_timer_sync() loops forever. Simple fix is to test if timer is pending. Fixes: 2235f2ac75fd ("inet: fix races with reqsk timers") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/inet_connection_sock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index b27fc401c6a9..e664706b350c 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -584,7 +584,7 @@ static bool reqsk_queue_unlink(struct request_sock_queue *queue, } spin_unlock(&queue->syn_wait_lock); - if (del_timer_sync(&req->rsk_timer)) + if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer)) reqsk_put(req); return found; } -- 2.4.3