Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934784AbdCJNZM (ORCPT ); Fri, 10 Mar 2017 08:25:12 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43601 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934641AbdCJLwg (ORCPT ); Fri, 10 Mar 2017 06:52:36 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "Eric Dumazet" , "Willem de Bruijn" Date: Fri, 10 Mar 2017 11:46:23 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 298/370] packet: fix races in fanout_add() In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1869 Lines: 74 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit d199fab63c11998a602205f7ee7ff7c05c97164b upstream. Multiple threads can call fanout_add() at the same time. We need to grab fanout_mutex earlier to avoid races that could lead to one thread freeing po->rollover that was set by another thread. Do the same in fanout_release(), for peace of mind, and to help us finding lockdep issues earlier. Fixes: dc99f600698d ("packet: Add fanout support.") Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller [bwh: Backported to 3.16: - No rollover queue stats - Adjust context] Signed-off-by: Ben Hutchings --- --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1451,13 +1451,16 @@ static int fanout_add(struct sock *sk, u return -EINVAL; } + mutex_lock(&fanout_mutex); + + err = -EINVAL; if (!po->running) - return -EINVAL; + goto out; + err = -EALREADY; if (po->fanout) - return -EALREADY; + goto out; - mutex_lock(&fanout_mutex); match = NULL; list_for_each_entry(f, &fanout_list, list) { if (f->id == id && @@ -1513,17 +1516,16 @@ static void fanout_release(struct sock * struct packet_sock *po = pkt_sk(sk); struct packet_fanout *f; - f = po->fanout; - if (!f) - return; - mutex_lock(&fanout_mutex); - po->fanout = NULL; + f = po->fanout; + if (f) { + po->fanout = NULL; - if (atomic_dec_and_test(&f->sk_ref)) { - list_del(&f->list); - dev_remove_pack(&f->prot_hook); - kfree(f); + if (atomic_dec_and_test(&f->sk_ref)) { + list_del(&f->list); + dev_remove_pack(&f->prot_hook); + kfree(f); + } } mutex_unlock(&fanout_mutex); }