From nobody Fri Dec 19 07:55:07 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EF33C00144 for ; Mon, 1 Aug 2022 12:03:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233145AbiHAMDa (ORCPT ); Mon, 1 Aug 2022 08:03:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233692AbiHAMBk (ORCPT ); Mon, 1 Aug 2022 08:01:40 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD9E452DE3; Mon, 1 Aug 2022 04:53:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E066DB81170; Mon, 1 Aug 2022 11:53:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52168C433C1; Mon, 1 Aug 2022 11:53:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1659354819; bh=WuhQ8glCoCgZcuHqBbEAvdh4TYzU60trc0vQAcMLLBY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Bf63rCi2RjREB1JRX4kXW/oX8PoYCNWTgcAZbRmwvwJMZVP94hZspIyqT01yJBNbT cg33THGbKk1SsnkBRzH8S2PoD0SaNJONgOA/64lUfI4Nkjvnzt8VjOGhTFSrsughuR AxPam/QZ7kiSytRBMwOk50flq37pEVcEdjbu/cd4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ziyang Xuan , David Ahern , Jakub Kicinski Subject: [PATCH 5.15 31/69] ipv6/addrconf: fix a null-ptr-deref bug for ip6_ptr Date: Mon, 1 Aug 2022 13:46:55 +0200 Message-Id: <20220801114135.774760661@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220801114134.468284027@linuxfoundation.org> References: <20220801114134.468284027@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Ziyang Xuan commit 85f0173df35e5462d89947135a6a5599c6c3ef6f upstream. Change net device's MTU to smaller than IPV6_MIN_MTU or unregister device while matching route. That may trigger null-ptr-deref bug for ip6_ptr probability as following. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D BUG: KASAN: null-ptr-deref in find_match.part.0+0x70/0x134 Read of size 4 at addr 0000000000000308 by task ping6/263 CPU: 2 PID: 263 Comm: ping6 Not tainted 5.19.0-rc7+ #14 Call trace: dump_backtrace+0x1a8/0x230 show_stack+0x20/0x70 dump_stack_lvl+0x68/0x84 print_report+0xc4/0x120 kasan_report+0x84/0x120 __asan_load4+0x94/0xd0 find_match.part.0+0x70/0x134 __find_rr_leaf+0x408/0x470 fib6_table_lookup+0x264/0x540 ip6_pol_route+0xf4/0x260 ip6_pol_route_output+0x58/0x70 fib6_rule_lookup+0x1a8/0x330 ip6_route_output_flags_noref+0xd8/0x1a0 ip6_route_output_flags+0x58/0x160 ip6_dst_lookup_tail+0x5b4/0x85c ip6_dst_lookup_flow+0x98/0x120 rawv6_sendmsg+0x49c/0xc70 inet_sendmsg+0x68/0x94 Reproducer as following: Firstly, prepare conditions: $ip netns add ns1 $ip netns add ns2 $ip link add veth1 type veth peer name veth2 $ip link set veth1 netns ns1 $ip link set veth2 netns ns2 $ip netns exec ns1 ip -6 addr add 2001:0db8:0:f101::1/64 dev veth1 $ip netns exec ns2 ip -6 addr add 2001:0db8:0:f101::2/64 dev veth2 $ip netns exec ns1 ifconfig veth1 up $ip netns exec ns2 ifconfig veth2 up $ip netns exec ns1 ip -6 route add 2000::/64 dev veth1 metric 1 $ip netns exec ns2 ip -6 route add 2001::/64 dev veth2 metric 1 Secondly, execute the following two commands in two ssh windows respectively: $ip netns exec ns1 sh $while true; do ip -6 addr add 2001:0db8:0:f101::1/64 dev veth1; ip -6 rout= e add 2000::/64 dev veth1 metric 1; ping6 2000::2; done $ip netns exec ns1 sh $while true; do ip link set veth1 mtu 1000; ip link set veth1 mtu 1500; sle= ep 5; done It is because ip6_ptr has been assigned to NULL in addrconf_ifdown() firstl= y, then ip6_ignore_linkdown() accesses ip6_ptr directly without NULL check. cpu0 cpu1 fib6_table_lookup __find_rr_leaf addrconf_notify [ NETDEV_CHANGEMTU ] addrconf_ifdown RCU_INIT_POINTER(dev->ip6_ptr, NULL) find_match ip6_ignore_linkdown So we can add NULL check for ip6_ptr before using in ip6_ignore_linkdown() = to fix the null-ptr-deref bug. Fixes: dcd1f572954f ("net/ipv6: Remove fib6_idev") Signed-off-by: Ziyang Xuan Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20220728013307.656257-1-william.xuanziyang@= huawei.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- include/net/addrconf.h | 3 +++ 1 file changed, 3 insertions(+) --- a/include/net/addrconf.h +++ b/include/net/addrconf.h @@ -403,6 +403,9 @@ static inline bool ip6_ignore_linkdown(c { const struct inet6_dev *idev =3D __in6_dev_get(dev); =20 + if (unlikely(!idev)) + return true; + return !!idev->cnf.ignore_routes_with_linkdown; }