Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755331AbcKNCLB (ORCPT ); Sun, 13 Nov 2016 21:11:01 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46342 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754610AbcKNCGV (ORCPT ); Sun, 13 Nov 2016 21:06:21 -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, "Matt Bennett" , "Guillaume Nault" , "Cyrill Gorcunov" , "David S. Miller" , linux-ppp@vger.kernel.org, "Paul Mackerras" , "WANG Cong" Date: Mon, 14 Nov 2016 00:14:07 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 014/152] ppp: defer netns reference release for ppp channel In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 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: 1824 Lines: 54 3.2.84-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: WANG Cong commit 205e1e255c479f3fd77446415706463b282f94e4 upstream. Matt reported that we have a NULL pointer dereference in ppp_pernet() from ppp_connect_channel(), i.e. pch->chan_net is NULL. This is due to that a parallel ppp_unregister_channel() could happen while we are in ppp_connect_channel(), during which pch->chan_net set to NULL. Since we need a reference to net per channel, it makes sense to sync the refcnt with the life time of the channel, therefore we should release this reference when we destroy it. Fixes: 1f461dcdd296 ("ppp: take reference on channels netns") Reported-by: Matt Bennett Cc: Paul Mackerras Cc: linux-ppp@vger.kernel.org Cc: Guillaume Nault Cc: Cyrill Gorcunov Signed-off-by: Cong Wang Reviewed-by: Cyrill Gorcunov Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- drivers/net/ppp/ppp_generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -2275,8 +2275,6 @@ ppp_unregister_channel(struct ppp_channe spin_lock_bh(&pn->all_channels_lock); list_del(&pch->list); spin_unlock_bh(&pn->all_channels_lock); - put_net(pch->chan_net); - pch->chan_net = NULL; pch->file.dead = 1; wake_up_interruptible(&pch->file.rwait); @@ -2883,6 +2881,9 @@ ppp_disconnect_channel(struct channel *p */ static void ppp_destroy_channel(struct channel *pch) { + put_net(pch->chan_net); + pch->chan_net = NULL; + atomic_dec(&channel_count); if (!pch->file.dead) {