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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0953C77B7C for ; Sun, 28 May 2023 19:24:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230029AbjE1TYp (ORCPT ); Sun, 28 May 2023 15:24:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230033AbjE1TYo (ORCPT ); Sun, 28 May 2023 15:24:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2BDD4D2 for ; Sun, 28 May 2023 12:24:43 -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 dfw.source.kernel.org (Postfix) with ESMTPS id BD68561BBB for ; Sun, 28 May 2023 19:24:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DAF2CC433D2; Sun, 28 May 2023 19:24:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1685301882; bh=76oDA74DjseX8EmqZ0PVg34ee78dUCKi14z9AFluXu8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vJr+5//kJvfDcGuKFHDXLMBYpqIl+pIi/qFwP3aELVERpSdMupSFcV/1tQLLVT+AH +5Z2leT9uel8nD1c9qxU4c6oVexdahGdZ4rWdhOn2oAtXG7Fx2vkfevtPpMP4hvEYs RfoRromOr+UCCv3HO+AlD2LvafrCZ471UrqHU85o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Feng Zhou , Cong Wang , Peilin Ye , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 066/161] ip6_gre: Fix skb_under_panic in __gre6_xmit() Date: Sun, 28 May 2023 20:09:50 +0100 Message-Id: <20230528190839.272304122@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230528190837.051205996@linuxfoundation.org> References: <20230528190837.051205996@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Stable-dep-of: d80fc101d2eb ("erspan: get the proto with the md version for collect_md") 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 85ec466b5735e..a1fd3c9c1da3e 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -720,9 +720,6 @@ 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; @@ -751,6 +748,9 @@ 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), @@ -761,6 +761,9 @@ 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)); -- 2.39.2