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 CEEB24F7CDC; Wed, 30 Sep 2026 15:42:30 +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=1790782955; cv=none; b=S+7bideHFRXW3Z59VOcx2p4kE83uxd/rasnFbHaVgGUrF69OGG74iHolHQM8gnCo82X0wsFCircAJq5OWZ7aqR+oriDjY7qWi0Gw8zSP0zQ1aAoOXEwwpK1tLOD1A5T7JQWHc0ZDx7V35bxN3aRewGgO0TqSNxXdyvolknRqxr8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790782955; c=relaxed/simple; bh=GnlHEweG3hX8uS5a0eX/UXYdTyBhrEG7o+iqZ06uWZQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jL4CgTWlhbtkzQ6vJF3hhy0v635bdO2Qx+WJtb6JWmVBaTh2ZSmPxZ5pFwjnaHjpxTObUg97lBntqoKkbQRb9N0tlusGa0eIH6DcJob5XFJ51holoHKYujROtjBw3U8yu3VQuYj21ruzlMYR+W+z/2WPqjSijYuiGwUK6tWES0Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pLbrzZto; 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="pLbrzZto" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5AC001F00898; Wed, 30 Sep 2026 15:42:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790782947; bh=9hcIS0QdnFt+aTVg5aMWBvWAViBF5rALIqcWOvqhsRo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=pLbrzZto5HzM3mBCyEsznPU4nnCqsY55a2gK6ehdwH1wFwEn0XnJzx9EWRnzjpnnt LUvb1fEblCCa9YIwHsZObyN+uz0FAcskQ+VxdePjD2LW0cr1syk+TYbfgtwB+R9zDQ A354y++PvDpcIuO4DQXiOkzAGKwl9I+FQBYVu12Q= 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 5.10 209/595] ipv6: sr: restore network header before routing and forwarding Date: Wed, 30 Sep 2026 17:21:42 +0200 Message-ID: <20260930152352.230791082@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152347.700140858@linuxfoundation.org> References: <20260930152347.700140858@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 5.10-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 0230fa98a3482..53b79a83e0e53 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -439,7 +439,7 @@ 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); @@ -465,7 +465,7 @@ 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