From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E4C1CA9EC2 for ; Tue, 29 Oct 2019 00:54:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71435218BA for ; Tue, 29 Oct 2019 00:54:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727441AbfJ2Ayb (ORCPT ); Mon, 28 Oct 2019 20:54:31 -0400 Received: from Chamillionaire.breakpoint.cc ([193.142.43.52]:55350 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727336AbfJ2Ayb (ORCPT ); Mon, 28 Oct 2019 20:54:31 -0400 Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1iPFmH-0000V8-1x; Tue, 29 Oct 2019 01:54:29 +0100 From: Florian Westphal To: Cc: syzbot+c54f457cad330e57e967@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, netfilter-devel@vger.kernel.org, Florian Westphal , Edward Cree Subject: [PATCH net-next] inet: do not call sublist_rcv on empty list Date: Tue, 29 Oct 2019 01:44:04 +0100 Message-Id: <20191029004404.8563-1-fw@strlen.de> X-Mailer: git-send-email 2.23.0 In-Reply-To: <0000000000003cc4980596006472@google.com> References: <0000000000003cc4980596006472@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org syzbot triggered struct net NULL deref in NF_HOOK_LIST: RIP: 0010:NF_HOOK_LIST include/linux/netfilter.h:331 [inline] RIP: 0010:ip6_sublist_rcv+0x5c9/0x930 net/ipv6/ip6_input.c:292 ipv6_list_rcv+0x373/0x4b0 net/ipv6/ip6_input.c:328 __netif_receive_skb_list_ptype net/core/dev.c:5274 [inline] Reason: void ipv6_list_rcv(struct list_head *head, struct packet_type *pt, struct net_device *orig_dev) [..] list_for_each_entry_safe(skb, next, head, list) { /* iterates list */ skb = ip6_rcv_core(skb, dev, net); /* ip6_rcv_core drops skb -> NULL is returned */ if (skb == NULL) continue; [..] } /* sublist is empty -> curr_net is NULL */ ip6_sublist_rcv(&sublist, curr_dev, curr_net); Before the recent change NF_HOOK_LIST did a list iteration before struct net deref, i.e. it was a no-op in the empty list case. List iteration now happens after *net deref, causing crash. Follow the same pattern as the ip(v6)_list_rcv loop and add a list_empty test for the final sublist dispatch too. Cc: Edward Cree Reported-by: syzbot+c54f457cad330e57e967@syzkaller.appspotmail.com Fixes: ca58fbe06c54 ("netfilter: add and use nf_hook_slow_list()") Signed-off-by: Florian Westphal --- net/ipv4/ip_input.c | 3 ++- net/ipv6/ip6_input.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c index c59a78a267c3..24a95126e698 100644 --- a/net/ipv4/ip_input.c +++ b/net/ipv4/ip_input.c @@ -611,5 +611,6 @@ void ip_list_rcv(struct list_head *head, struct packet_type *pt, list_add_tail(&skb->list, &sublist); } /* dispatch final sublist */ - ip_sublist_rcv(&sublist, curr_dev, curr_net); + if (!list_empty(&sublist)) + ip_sublist_rcv(&sublist, curr_dev, curr_net); } diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c index 3d71c7d6102c..ef7f707d9ae3 100644 --- a/net/ipv6/ip6_input.c +++ b/net/ipv6/ip6_input.c @@ -325,7 +325,8 @@ void ipv6_list_rcv(struct list_head *head, struct packet_type *pt, list_add_tail(&skb->list, &sublist); } /* dispatch final sublist */ - ip6_sublist_rcv(&sublist, curr_dev, curr_net); + if (!list_empty(&sublist)) + ip6_sublist_rcv(&sublist, curr_dev, curr_net); } INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *)); -- 2.23.0