From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [Patch net] ppp: defer netns reference release for ppp channel Date: Tue, 5 Jul 2016 22:12:36 -0700 Message-ID: <1467781956-2229-1-git-send-email-xiyou.wangcong@gmail.com> Cc: Matt.Bennett@alliedtelesis.co.nz, Cong Wang , Paul Mackerras , linux-ppp@vger.kernel.org, Guillaume Nault , Cyrill Gorcunov To: netdev@vger.kernel.org Return-path: Received: from mail-pf0-f193.google.com ([209.85.192.193]:35413 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751674AbcGFFOn (ORCPT ); Wed, 6 Jul 2016 01:14:43 -0400 Sender: netdev-owner@vger.kernel.org List-ID: 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 --- drivers/net/ppp/ppp_generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 8dedafa..a30ee42 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -2601,8 +2601,6 @@ ppp_unregister_channel(struct ppp_channel *chan) 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); @@ -3136,6 +3134,9 @@ ppp_disconnect_channel(struct channel *pch) */ 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) { -- 1.8.4.5