From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 738A434F48B; Tue, 26 Aug 2025 14:12:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756217527; cv=none; b=NHVaRubqy0sh+WqBw05LKXJ935eCdkp5l+6Y+ZhO6ab8IASA9xRQpT3/9DPwAq61gyemMGaz8dqqNy2U62nNwEkWyncDvhcVlkOTwiPt7mOOV0Y3N6RZEZhHj9QpuPkh1KAF1JbiNcwc0IeYlzaKOl55akpPvgS80a0nRxsmnMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756217527; c=relaxed/simple; bh=OtNwsaw8UzkL2nv/gYvK2/62XR+p8aaT8gHN55620yw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TN0l8vn6FXgBpwm+AES/n0jrM9SN1SgGlYUutgiTSKCTSaq0NpQ4Karp0u3u0zeg17KR8q83wJaMNjQ8C7LlBD8FXV8Spybgpy6anbh9LTiYQiIVqyYWKiro7qdOC17Wtk2nhWSmsxHxdW8m5w/Ns+ZNHNPLM/6kA7guWIYP2kY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=z5XTzSnq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="z5XTzSnq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E9D2DC4CEF1; Tue, 26 Aug 2025 14:12:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756217527; bh=OtNwsaw8UzkL2nv/gYvK2/62XR+p8aaT8gHN55620yw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=z5XTzSnqfXs3kJ1NuiOLszD7w5KTY822kgcoV4e2TZ4qfCQX1eOSRcpRevwXGm8sF fSYPKcQsykdV4+yOgxW8tsVbqpfnwEKZeoOpNZE1lJAQRpTmbHVXc7ONCfsef4PJKA L22qaPBZnPAM7DncaJi1oCVehD6fZ35LOHWWQ2E4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+af43e647fd835acc02df@syzkaller.appspotmail.com, Eric Dumazet , Dawid Osuchowski , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10 177/523] ipv6: reject malicious packets in ipv6_gso_segment() Date: Tue, 26 Aug 2025 13:06:27 +0200 Message-ID: <20250826110928.824353638@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110924.562212281@linuxfoundation.org> References: <20250826110924.562212281@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d45cf1e7d7180256e17c9ce88e32e8061a7887fe ] 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 Reviewed-by: Dawid Osuchowski Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250730131738.3385939-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- 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 3248e4aeec03..ca7f2a2c3e3f 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2519,6 +2519,29 @@ static inline void skb_reset_transport_header(struct sk_buff *skb) skb->transport_header = skb->data - skb->head; } +/** + * 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 673f02ea62aa..c145be2fd6e4 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -111,7 +111,9 @@ 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; -- 2.39.5