From: Eric Dumazet Date: Thu, 13 Aug 2015 22:44:51 +0000 (-0700) Subject: inet: fix potential deadlock in reqsk_queue_unlink() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=83fccfc3940c4a2db90fd7e7079f5b465cd8c6af;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git 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 --- diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 05e3145f7dc3..134957159c27 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -593,7 +593,7 @@ 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; }