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 EC85E25A321; Wed, 8 Apr 2026 18:52:04 +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=1775674325; cv=none; b=tw61InOTPAurO/71ZXOid+RVp4MQfjwd44VM+Mo+HGqlYoB5rTyuTkANK3jmj1xuFOyb09W2sWGdbDjUBMqPwepkXRkaLeEArCbRMfxd7yclBvWZG4eNGzUZa3BFdEhesqrAruZle4I4pFZ6uPNNF/hw3zXcSQZYr7yh7qZAC3c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775674325; c=relaxed/simple; bh=kvMho+YHdlMb8aqVys63W0OX7xqIjRhkBuwxV1ImGtI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gW95AkPkezC66iYxKUh0tnWcZ3q/6/ctjvNxbstYDWIyBk7wcjOpoQuYidRThmvmziB1BzquPnDw3/hl2cJrualXmAxFS+d5sElCSWmyzoF+z+zNHDyAw+Ny2pT9J28vFZnjhCs2zwuFSY6dVxf004H4/gvqtRGGfYmDxrF3q7w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FRhFQKZb; 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="FRhFQKZb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 805F5C19421; Wed, 8 Apr 2026 18:52:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775674324; bh=kvMho+YHdlMb8aqVys63W0OX7xqIjRhkBuwxV1ImGtI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FRhFQKZbIQNo00cy5h1lqLoosEvwVAXp/1L5beGQwIjbxrafhJy1p7LCNH/kFC/Vp HXRKhKD35kbv+akGm0u8coNxHVuu724JhZoWhELSuZvWcuuJBKzRtutPoDj6LNJ9rc 5ozcPSCHIHsuMjLFUPyXyXaMQpHHooJ1qEF/Pw3I= 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 6.19 053/311] ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Date: Wed, 8 Apr 2026 20:00:53 +0200 Message-ID: <20260408175941.396181460@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175939.393281918@linuxfoundation.org> References: <20260408175939.393281918@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 6.19-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 0f41ca6f3d83e..9844758252718 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -871,6 +871,9 @@ 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