Commit 2306c704 authored Oct 01, 2015 by Eric Dumazet Committed by David S. Miller Oct 05, 2015

inet: fix race in reqsk_queue_unlink()



reqsk_timer_handler() tests if icsk_accept_queue.listen_opt
is NULL at its beginning.

By the time it calls inet_csk_reqsk_queue_drop() and
reqsk_queue_unlink(), listener might have been closed and
inet_csk_listen_stop() had called reqsk_queue_yank_acceptq()
which sets icsk_accept_queue.listen_opt to NULL

We therefore need to correctly check listen_opt being NULL
after holding syn_wait_lock for proper synchronization.

Fixes: fa76ce73 ("inet: get rid of central tcp/dccp listener timer")
Fixes: b357a364 ("inet: fix possible panic in reqsk_queue_unlink()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8695a144

net/ipv4/inet_connection_sock.c

+10 −9

Original line number	Diff line number	Diff line
		@@ -577,12 +577,13 @@ EXPORT_SYMBOL(inet_rtx_syn_ack);
		static bool reqsk_queue_unlink(struct request_sock_queue *queue,
		struct request_sock *req)
		{
		struct listen_sock *lopt = queue->listen_opt;
		struct request_sock **prev;
		struct listen_sock *lopt;
		bool found = false;

		spin_lock(&queue->syn_wait_lock);

		lopt = queue->listen_opt;
		if (lopt) {
		for (prev = &lopt->syn_table[req->rsk_hash]; *prev != NULL;
		prev = &(*prev)->dl_next) {
		if (*prev == req) {
		@@ -591,7 +592,7 @@ static bool reqsk_queue_unlink(struct request_sock_queue *queue,
		break;
		}
		}

		}
		spin_unlock(&queue->syn_wait_lock);
		if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
		reqsk_put(req);