From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f74.google.com (mail-qv1-f74.google.com [209.85.219.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B708A172BB9 for ; Wed, 30 Jul 2025 13:17:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881463; cv=none; b=D3uIIaybrpQiRZj6kcMzxdnBzPsLbAJfPIU0r8XGY+j6xhH8xmC2Vb/XWqJ6Z74rjmEBGHhn6FV7yxOX0uFW2YoeX3VNIoE4Zbsij6tbPKRVMqpScdPlJ1UD6u2RvU476VJ4CXvErHhE80EoJKOo9kUCww+FFt7Y+Z45uyYnQzA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881463; c=relaxed/simple; bh=wQV51C2Ib2mpJndbb6jmRVEky7r53Y8+vIDYD2N93es=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=dT/Zwts6Q+n3olKumPtHSjhGi6JgeaL8WDToKDhEcaw8cltEq4OvEYG5D2F0PsSMcN3nLWstenlDdcL9Q4IBlC/xPBqx9I0AWcfPH4uU68oPJzhl8bH3x0o5/cIVKyIWRdBwVUbXbo/Vgfmbg0Xa6Z7dwcmwt5yBYQgErJD8gIc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=OsMyF18B; arc=none smtp.client-ip=209.85.219.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="OsMyF18B" Received: by mail-qv1-f74.google.com with SMTP id 6a1803df08f44-707453b0307so60365366d6.3 for ; Wed, 30 Jul 2025 06:17:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1753881460; x=1754486260; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=2ZJgGJWQFeclQw2uoRHesjGOwX1lqWpTyzoKd2zAekY=; b=OsMyF18BO0vf3nOVASswfO5OkxPa4u9K8F1sPsgWBs8mR6twi+VDrfHbVRPkWPmTFX +PIf/Q71C42uCT+rpyxzMUSPJGBCkd0Q3B5wyl0OjHLyU5933Q3Ht6mmSzmdWxCtxIyb PdNt7dHzW3+iJWmbuOoOtdUW77ibVTdTTQLQeiQQMVs8fWgvPOdAaTsS1ag3f1EZFAdh r6DOc8dX0RVS2it+3/xo8KsR1Xvpfd7lBQt2JhEuN7nHrMrL6NXUaHNCO5SnMfDCQFP9 RyLz/Jz1k4x6ndeYWxqqGjxsi/4ZupjF7v/zUZt8mN9AGJUqb6g59KPuLqMzckZUmQ3n Skng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1753881460; x=1754486260; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=2ZJgGJWQFeclQw2uoRHesjGOwX1lqWpTyzoKd2zAekY=; b=PZGTZAEjmZn0rDw9ZlqxnUJ8Ei6+P+/BfZZdRHR6+xw5NEHKNdQDXWr5MeTZViYT4V 22CN4PdYMK8zJyz/ICAI1IBvEdlA58pH+NOCuvlW83tvoziFkGv0BNPSOu4UMDzgEvrE fKMnHjhQESHxGvc/ut3IiU2d7NWrbizTmvIOzyBLBR8AOpzMmivoskkVdpHNR79LeMBG MIlLHYfYcJr9ugG5sf/QF7xdsg7KBMp3EclYMCvbKTL10KDtYDRIqGnLOHJHZfMbz//b q4M+cCxGsQEIqspE/ZRFxu3MEWzrpZ1BBx5ky/Qn5eXz/xm/24xLRaJuTD0QJ5wPLqjL B11A== X-Forwarded-Encrypted: i=1; AJvYcCUZJtD9qDTO7FbYZt+YFQ0JEZXAE5LT0HgH4TeWR1V2oOZJeU1GvNXMrXRsLrQ1Y21hSHEO830=@vger.kernel.org X-Gm-Message-State: AOJu0YxSI7IoMOyqA9BUGxNIelb1KKP2mQF2DWOPxnIBGhs6Z7h9hbJo kgoccitCz9e1vmLPDIPr89BvK5X0tPwYgk/UsebVnqDDOjA46cTpQQcElvaYA6IhqPvBYzqlYeN OYgLcRS/4oXPTaA== X-Google-Smtp-Source: AGHT+IGOCBp8/tEEgbLplTinmZ3fumFDewMGJumvdHnr+/W4EklHcimHcrSwWX2SqQhV6dfvZwiF9VDrEgtfZg== X-Received: from qvblb13.prod.google.com ([2002:a05:6214:318d:b0:707:3161:5d79]) (user=edumazet job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6214:401a:b0:707:5671:c95e with SMTP id 6a1803df08f44-70767113d4emr46967526d6.27.1753881460258; Wed, 30 Jul 2025 06:17:40 -0700 (PDT) Date: Wed, 30 Jul 2025 13:17:38 +0000 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.50.1.552.g942d659e1b-goog Message-ID: <20250730131738.3385939-1-edumazet@google.com> Subject: [PATCH net] ipv6: reject malicious packets in ipv6_gso_segment() From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Willem de Bruijn , David Ahern , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet , syzbot+af43e647fd835acc02df@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" syzbot was able to craft a packet with very long IPv6 extension headers leading to an overflow of skb->transport_header. This 16bit field has a limited range. Add skb_reset_transport_header_careful() helper and use it from ipv6_gso_segment() WARNING: CPU: 0 PID: 5871 at ./include/linux/skbuff.h:3032 skb_reset_transport_header include/linux/skbuff.h:3032 [inline] WARNING: CPU: 0 PID: 5871 at ./include/linux/skbuff.h:3032 ipv6_gso_segment+0x15e2/0x21e0 net/ipv6/ip6_offload.c:151 Modules linked in: CPU: 0 UID: 0 PID: 5871 Comm: syz-executor211 Not tainted 6.16.0-rc6-syzkaller-g7abc678e3084 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:skb_reset_transport_header include/linux/skbuff.h:3032 [inline] RIP: 0010:ipv6_gso_segment+0x15e2/0x21e0 net/ipv6/ip6_offload.c:151 Call Trace: skb_mac_gso_segment+0x31c/0x640 net/core/gso.c:53 nsh_gso_segment+0x54a/0xe10 net/nsh/nsh.c:110 skb_mac_gso_segment+0x31c/0x640 net/core/gso.c:53 __skb_gso_segment+0x342/0x510 net/core/gso.c:124 skb_gso_segment include/net/gso.h:83 [inline] validate_xmit_skb+0x857/0x11b0 net/core/dev.c:3950 validate_xmit_skb_list+0x84/0x120 net/core/dev.c:4000 sch_direct_xmit+0xd3/0x4b0 net/sched/sch_generic.c:329 __dev_xmit_skb net/core/dev.c:4102 [inline] __dev_queue_xmit+0x17b6/0x3a70 net/core/dev.c:4679 Fixes: d1da932ed4ec ("ipv6: Separate ipv6 offload support") Reported-by: syzbot+af43e647fd835acc02df@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/688a1a05.050a0220.5d226.0008.GAE@google.com/T/#u Signed-off-by: Eric Dumazet --- include/linux/skbuff.h | 23 +++++++++++++++++++++++ net/ipv6/ip6_offload.c | 4 +++- 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index b8b06e71b73ea3fb5210239f585f4ba714395fd7..14b923ddb6dfcc3c031a7c9e4cb5fc4171424616 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -3033,6 +3033,29 @@ static inline void skb_reset_transport_header(struct sk_buff *skb) skb->transport_header = offset; } +/** + * skb_reset_transport_header_careful - conditionally reset transport header + * @skb: buffer to alter + * + * Hardened version of skb_reset_transport_header(). + * + * Returns: true if the operation was a success. + */ +static inline bool __must_check +skb_reset_transport_header_careful(struct sk_buff *skb) +{ + long offset = skb->data - skb->head; + + if (unlikely(offset != (typeof(skb->transport_header))offset)) + return false; + + if (unlikely(offset == (typeof(skb->transport_header))~0U)) + return false; + + skb->transport_header = offset; + return true; +} + static inline void skb_set_transport_header(struct sk_buff *skb, const int offset) { diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c index 9822163428b028d6dbf3f48abe4674bd6c581725..fce91183797a60fcbf271c73e086aeb0aa9d40c6 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -148,7 +148,9 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb, ops = rcu_dereference(inet6_offloads[proto]); if (likely(ops && ops->callbacks.gso_segment)) { - skb_reset_transport_header(skb); + if (!skb_reset_transport_header_careful(skb)) + goto out; + segs = ops->callbacks.gso_segment(skb, features); if (!segs) skb->network_header = skb_mac_header(skb) + nhoff - skb->head; -- 2.50.1.552.g942d659e1b-goog