From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 590B33AFAE2; Wed, 30 Sep 2026 19:04:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795058; cv=none; b=fK36IFWZ3i+oRe3giqqEsFnD3XqXL/5dnuk3LD519tRM9w7K010hiMu/qL0yXPFgDF4pqEtwP/5KGT9lxvhG78c3zsYGkjowPU6FIIPPWIIgnY2T3RQRavxMiOI/DkzBFP/PkDl97hir7FoM7qcORuYIqIg0iWuGvAyfE3btd6M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795058; c=relaxed/simple; bh=3FE3lb5SIC2EIbxrxpjAH3zaMEF2svscT9qNGiY4+Wo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IAfL4Jw17/6PHa9OEF4g+vxEPRpIV4BcLXz21Eu7mzyMtUYLd1Nrs9Xl300y4J5hTIPl5rEgJVU3r75Fapx9fqzXlMgVzDbu4eTmWP69HtX1iH3EzbR4MkDbAxymDaH8Ws2zvs+vM57+ZE+j9qeTfxn//LB7YYSgeDAJoE8HMt4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=KgRLSYGg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="KgRLSYGg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4D9F1F000FF; Wed, 30 Sep 2026 19:04:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790795057; bh=7YmlLbMOCdkgNQzajRpg8XgEE3Yv7k2FutHzty+XCzo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=KgRLSYGg1rcjRRZzcFvtt52fZ+CRw9PtfT1qyXU417Ynua+raNCAisfGYxeupwtrr w8YYX/j9iYbDlDLiruDCHdKauXGvnFmoVE4f2/+5gXbM0iqob1rpIKgjAIQxmkGdVd 2qYeaPxzdPKrsT8ffjJSpPihUzY8vHBMP/YlUS1I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, TencentOS Corvus AI , Jun Yang , Fourie Zhang , Eric Dumazet , Ido Schimmel , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 0429/1193] ipv6: sr: restore network header before routing and forwarding Date: Wed, 30 Sep 2026 17:18:33 +0200 Message-ID: <20260930152443.728213881@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@linuxfoundation.org> User-Agent: quilt/0.69 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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 975b5b067f525a1b1338c4a3bee1c46545801518 ] ipv6_srh_rcv() runs with skb->data at the Segment Routing Header (SRH) while skb_network_header() points at the IPv6 header. When segments_left > 0, ipv6_srh_rcv() previously restored the skb->data position by pushing sizeof(struct ipv6hdr), assuming the SRH immediately followed the fixed IPv6 header. If another extension header (such as a Hop-by-Hop options header) precedes the SRH, skb_network_offset() remained negative. This led to two problems: 1. During ip6_route_input(), fib6_rules_early_flow_dissect() invokes __skb_flow_dissect() which passes the negative skb_network_offset() to flow dissection, breaking BPF and C flow dissector logic. 2. If forwarded via ip6_forward() or redirected via act_mirred, downstream handlers (like sch_fragment() or neighbour output) pass the negative offset as an unsigned length, triggering OOB memcpy or buffer overflows. Fix this by pushing -skb_network_offset(skb) before routing, ensuring skb_network_offset(skb) is 0 for route lookup / flow dissection as well as downstream forwarding. On the loopback path, pull skb_transport_offset(skb) to restore skb->data to the SRH before looping back. Fixes: 1ababeba4a21 ("ipv6: implement dataplane support for rthdr type 4 (Segment Routing Header)") Reported-by: TencentOS Corvus AI Reported-by: Jun Yang Reported-by: Fourie Zhang Closes: https://lore.kernel.org/netdev/20260817104128.22681-1-juny24602@gmail.com/ Closes: https://lore.kernel.org/netdev/20260827092345.2301937-1-fouriezhang@tencent.com/ Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260828141727.2372570-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/exthdrs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c index e024d8da431c4..6b4cdc7745e85 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -454,7 +454,7 @@ static int ipv6_srh_rcv(struct sk_buff *skb) hdr->segments_left--; addr = hdr->segments + hdr->segments_left; - skb_push(skb, sizeof(struct ipv6hdr)); + skb_push(skb, -skb_network_offset(skb)); if (skb->ip_summed == CHECKSUM_COMPLETE) seg6_update_csum(skb); @@ -478,7 +478,7 @@ static int ipv6_srh_rcv(struct sk_buff *skb) } ipv6_hdr(skb)->hop_limit--; - skb_pull(skb, sizeof(struct ipv6hdr)); + skb_pull(skb, skb_transport_offset(skb)); goto looped_back; } -- 2.53.0