From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Yuchung Cheng , "David S. Miller" Subject: [PATCH 4.2 12/54] inet: fix race in reqsk_queue_unlink() Date: Fri, 23 Oct 2015 10:44:48 -0700 Message-Id: <20151023174519.469437032@linuxfoundation.org> In-Reply-To: <20151023174519.086915553@linuxfoundation.org> References: <20151023174519.086915553@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 2306c704ce280c97a60d1f45333b822b40281dea ] 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: fa76ce7328b2 ("inet: get rid of central tcp/dccp listener timer") Fixes: b357a364c57c ("inet: fix possible panic in reqsk_queue_unlink()") Signed-off-by: Eric Dumazet Cc: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/inet_connection_sock.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -577,21 +577,22 @@ 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); - - for (prev = &lopt->syn_table[req->rsk_hash]; *prev != NULL; - prev = &(*prev)->dl_next) { - if (*prev == req) { - *prev = req->dl_next; - found = true; - break; + lopt = queue->listen_opt; + if (lopt) { + for (prev = &lopt->syn_table[req->rsk_hash]; *prev != NULL; + prev = &(*prev)->dl_next) { + if (*prev == req) { + *prev = req->dl_next; + found = true; + break; + } } } - spin_unlock(&queue->syn_wait_lock); if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer)) reqsk_put(req);