From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754080AbdH1Ihk (ORCPT ); Mon, 28 Aug 2017 04:37:40 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34706 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753978AbdH1IOL (ORCPT ); Mon, 28 Aug 2017 04:14:11 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Dmitry Vyukov , "David S. Miller" Subject: [PATCH 4.4 04/53] ipv4: fix NULL dereference in free_fib_info_rcu() Date: Mon, 28 Aug 2017 10:05:09 +0200 Message-Id: <20170828080517.803064498@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170828080517.599193891@linuxfoundation.org> References: <20170828080517.599193891@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 187e5b3ac84d3421d2de3aca949b2791fbcad554 ] If fi->fib_metrics could not be allocated in fib_create_info() we attempt to dereference a NULL pointer in free_fib_info_rcu() : m = fi->fib_metrics; if (m != &dst_default_metrics && atomic_dec_and_test(&m->refcnt)) kfree(m); Before my recent patch, we used to call kfree(NULL) and nothing wrong happened. Instead of using RCU to defer freeing while we are under memory stress, it seems better to take immediate action. This was reported by syzkaller team. Fixes: 3fb07daff8e9 ("ipv4: add reference counting to metrics") Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/fib_semantics.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -1044,15 +1044,17 @@ struct fib_info *fib_create_info(struct fi = kzalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL); if (!fi) goto failure; - fib_info_cnt++; if (cfg->fc_mx) { fi->fib_metrics = kzalloc(sizeof(*fi->fib_metrics), GFP_KERNEL); - if (!fi->fib_metrics) - goto failure; + if (unlikely(!fi->fib_metrics)) { + kfree(fi); + return ERR_PTR(err); + } atomic_set(&fi->fib_metrics->refcnt, 1); - } else + } else { fi->fib_metrics = (struct dst_metrics *)&dst_default_metrics; - + } + fib_info_cnt++; fi->fib_net = net; fi->fib_protocol = cfg->fc_protocol; fi->fib_scope = cfg->fc_scope;