From patchwork Tue Apr 26 08:20:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 566650 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 E7669C433FE for ; Tue, 26 Apr 2022 08:38:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235466AbiDZIlL (ORCPT ); Tue, 26 Apr 2022 04:41:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241862AbiDZIjv (ORCPT ); Tue, 26 Apr 2022 04:39:51 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E235D14D28C; Tue, 26 Apr 2022 01:32:36 -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 5DE8AB81D06; Tue, 26 Apr 2022 08:32:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E31EC385AC; Tue, 26 Apr 2022 08:32:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650961954; bh=BU1pOQ1nK3rdoZZKFHeBNw6ys46RrHzncOALM+liBxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ELsOuhUixEDeUmg8RAZOmcjXaNyC74bEHLP11NqQ34k81iXH5S/ZJl9+C7NnDaK/O vhhVSryN26o9KKOMJpywJJ47mnN3Cj09vseI8RVnkDjiG9OHlH+KEICF6qyqoC08Tb mBreS6VxCGAncLlD8N9yYjBGTimj62W4pp09uJ1U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Feng Zhou , Cong Wang , Peilin Ye , "David S. Miller" , Sasha Levin Subject: [PATCH 5.10 23/86] ip6_gre: Fix skb_under_panic in __gre6_xmit() Date: Tue, 26 Apr 2022 10:20:51 +0200 Message-Id: <20220426081741.880255898@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220426081741.202366502@linuxfoundation.org> References: <20220426081741.202366502@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peilin Ye [ Upstream commit ab198e1d0dd8dc4bc7575fb50758e2cbd51e14e1 ] Feng reported an skb_under_panic BUG triggered by running test_ip6gretap() in tools/testing/selftests/bpf/test_tunnel.sh: [ 82.492551] skbuff: skb_under_panic: text:ffffffffb268bb8e len:403 put:12 head:ffff9997c5480000 data:ffff9997c547fff8 tail:0x18b end:0x2c0 dev:ip6gretap11 <...> [ 82.607380] Call Trace: [ 82.609389] [ 82.611136] skb_push.cold.109+0x10/0x10 [ 82.614289] __gre6_xmit+0x41e/0x590 [ 82.617169] ip6gre_tunnel_xmit+0x344/0x3f0 [ 82.620526] dev_hard_start_xmit+0xf1/0x330 [ 82.623882] sch_direct_xmit+0xe4/0x250 [ 82.626961] __dev_queue_xmit+0x720/0xfe0 <...> [ 82.633431] packet_sendmsg+0x96a/0x1cb0 [ 82.636568] sock_sendmsg+0x30/0x40 <...> The following sequence of events caused the BUG: 1. During ip6gretap device initialization, tunnel->tun_hlen (e.g. 4) is calculated based on old flags (see ip6gre_calc_hlen()); 2. packet_snd() reserves header room for skb A, assuming tunnel->tun_hlen is 4; 3. Later (in clsact Qdisc), the eBPF program sets a new tunnel key for skb A using bpf_skb_set_tunnel_key() (see _ip6gretap_set_tunnel()); 4. __gre6_xmit() detects the new tunnel key, and recalculates "tun_hlen" (e.g. 12) based on new flags (e.g. TUNNEL_KEY and TUNNEL_SEQ); 5. gre_build_header() calls skb_push() with insufficient reserved header room, triggering the BUG. As sugguested by Cong, fix it by moving the call to skb_cow_head() after the recalculation of tun_hlen. Reproducer: OBJ=$LINUX/tools/testing/selftests/bpf/test_tunnel_kern.o ip netns add at_ns0 ip link add veth0 type veth peer name veth1 ip link set veth0 netns at_ns0 ip netns exec at_ns0 ip addr add 172.16.1.100/24 dev veth0 ip netns exec at_ns0 ip link set dev veth0 up ip link set dev veth1 up mtu 1500 ip addr add dev veth1 172.16.1.200/24 ip netns exec at_ns0 ip addr add ::11/96 dev veth0 ip netns exec at_ns0 ip link set dev veth0 up ip addr add dev veth1 ::22/96 ip link set dev veth1 up ip netns exec at_ns0 \ ip link add dev ip6gretap00 type ip6gretap seq flowlabel 0xbcdef key 2 \ local ::11 remote ::22 ip netns exec at_ns0 ip addr add dev ip6gretap00 10.1.1.100/24 ip netns exec at_ns0 ip addr add dev ip6gretap00 fc80::100/96 ip netns exec at_ns0 ip link set dev ip6gretap00 up ip link add dev ip6gretap11 type ip6gretap external ip addr add dev ip6gretap11 10.1.1.200/24 ip addr add dev ip6gretap11 fc80::200/24 ip link set dev ip6gretap11 up tc qdisc add dev ip6gretap11 clsact tc filter add dev ip6gretap11 egress bpf da obj $OBJ sec ip6gretap_set_tunnel tc filter add dev ip6gretap11 ingress bpf da obj $OBJ sec ip6gretap_get_tunnel ping6 -c 3 -w 10 -q ::11 Fixes: 6712abc168eb ("ip6_gre: add ip6 gre and gretap collect_md mode") Reported-by: Feng Zhou Co-developed-by: Cong Wang Signed-off-by: Cong Wang Signed-off-by: Peilin Ye Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv6/ip6_gre.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 949d6fbc1ca0..1f6c752f13b4 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -733,9 +733,6 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb, else fl6->daddr = tunnel->parms.raddr; - if (skb_cow_head(skb, dev->needed_headroom ?: tunnel->hlen)) - return -ENOMEM; - /* Push GRE header. */ protocol = (dev->type == ARPHRD_ETHER) ? htons(ETH_P_TEB) : proto; @@ -763,6 +760,9 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb, (TUNNEL_CSUM | TUNNEL_KEY | TUNNEL_SEQ); tun_hlen = gre_calc_hlen(flags); + if (skb_cow_head(skb, dev->needed_headroom ?: tun_hlen + tunnel->encap_hlen)) + return -ENOMEM; + gre_build_header(skb, tun_hlen, flags, protocol, tunnel_id_to_key32(tun_info->key.tun_id), @@ -773,6 +773,9 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb, if (tunnel->parms.o_flags & TUNNEL_SEQ) tunnel->o_seqno++; + if (skb_cow_head(skb, dev->needed_headroom ?: tunnel->hlen)) + return -ENOMEM; + gre_build_header(skb, tunnel->tun_hlen, tunnel->parms.o_flags, protocol, tunnel->parms.o_key, htonl(tunnel->o_seqno));