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 F2F3C324B1F; Wed, 8 Apr 2026 18:21:20 +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=1775672481; cv=none; b=BbAHqSVdmAqVM+2viLr34R2fwEmiEfvgpF+Bl+uY8d7Qf/Fuufcp4MS5aIcRXIqBaGST7+UN1esmerhwPd5XCgnObidc7wqZeyYdYZhHK0vFdOg+BW/pmuJxmorMVd+mA5W+r1A7TVba/hFwDPMuyfs/0YXWGNsmfdJQa/ET1bw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775672481; c=relaxed/simple; bh=SeafxZw7k9fNF4cCWcDIO3yHRKSSvRxJt5nyB8vDazc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lp40z1G+p2fGDYdn0pb9uBMSXBUJvWsMg+A/mnRA1puVE/DpuOwxb8OwEa4CC1woAkKa9DZhm5jjTcmnx1hgeviD67AewR1OxuzU4gf1C/lnqBbCSWVlao37zXgTKX/FrTIyK9mPBvaSNzXD3PRiJHvi4w3cCUEnf6LVU4WekqM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eIpc9bR0; 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="eIpc9bR0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 892E2C19421; Wed, 8 Apr 2026 18:21:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775672480; bh=SeafxZw7k9fNF4cCWcDIO3yHRKSSvRxJt5nyB8vDazc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eIpc9bR0Bz4sEWtEJFnQsL5G38RfDN0iq8pE9th6ZiTa43wVDKfK7nXkMXJCw+Pbm GAeBJPOmALmPXGtI1b2161PplvtkLfVEHvaQgKhzHrQfETpvYQLH+nL0Dmv4JpCc0g XzxBWeY160mn+J1Cy2b3fDYr951d96TbF4ESZUig= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ido Schimmel , Eric Dumazet , Oskar Kjos , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 023/160] ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Date: Wed, 8 Apr 2026 20:01:50 +0200 Message-ID: <20260408175914.068077276@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175913.177092714@linuxfoundation.org> References: <20260408175913.177092714@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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 86ab3e55673a7a49a841838776f1ab18d23a67b5 ] Sashiko AI-review observed: In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2 and passed to icmp6_send(), it uses IP6CB(skb2). IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm at offset 18. If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO). This would scan the inner, attacker-controlled IPv6 packet starting at that offset, potentially returning a fake TLV without checking if the remaining packet length can hold the full 18-byte struct ipv6_destopt_hao. Could mip6_addr_swap() then perform a 16-byte swap that extends past the end of the packet data into skb_shared_info? Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and ip6ip6_err() to prevent this? This patch implements the first suggestion. I am not sure if ip6ip6_err() needs to be changed. A separate patch would be better anyway. Fixes: ca15a078bd90 ("sit: generate icmpv6 error when receiving icmpv4 error") Reported-by: Ido Schimmel Closes: https://sashiko.dev/#/patchset/20260326155138.2429480-1-edumazet%40google.com Signed-off-by: Eric Dumazet Cc: Oskar Kjos Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260326202608.2976021-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/icmp.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c index 1d1c56e0e2460..0002fe04e0409 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -679,6 +679,9 @@ int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs, int type, if (!skb2) return 1; + /* Remove debris left by IPv4 stack. */ + memset(IP6CB(skb2), 0, sizeof(*IP6CB(skb2))); + skb_dst_drop(skb2); skb_pull(skb2, nhs); skb_reset_network_header(skb2); -- 2.53.0