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 162373B0AFC; Wed, 8 Apr 2026 18:41:23 +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=1775673684; cv=none; b=n+ZkrBo3j3mwic5cTcYoQ1zkYez3VRPnNfdUBJS0OJjvrPAmyeSbcTiTHhqoi1QHZrmYQI2eTzJljnKiNO9BllPyLh9FPkjG+W+Q2BiJ74XSAZBclSfERDOvT4/AcmqDinLStiSgHaTc2QT4dL+n8M4ZvQwR/UDwLD4596nG/k0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775673684; c=relaxed/simple; bh=yoq/FgCXm0Us15A6r5sL5HH3XDEcMu88ee/8PD7Ag2Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hqryfxpj8HxXpHaeM3qQ9VwJn+wtlelMM51OqxNiTS0YZsVtESME4dgZ9thbnxNxxg5XwjIi/AMaOG9QmlcFXPjprFedu5Xlr8zLvSzmSjyNjoXrSA9pUDf3Dc4ZpGU28rbi4NmmfBSh/IZ3xzr/D0D2SYe5H/p2D3keGIi7byg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=fI0V/wQ2; 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="fI0V/wQ2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4812CC19421; Wed, 8 Apr 2026 18:41:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775673683; bh=yoq/FgCXm0Us15A6r5sL5HH3XDEcMu88ee/8PD7Ag2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fI0V/wQ2dHhB702NmgoR+vMQifGOa6VROpkzlJs7kKHoU6c71nH+NpOajSotTZGpC S/JDc7NxL6GBYp4ud6YHdDhR7gdALIpd5L3gUl6zlpiiSlW6DPhWk3d8noFLAYHJCt R35HG0kdnJ1zKNxnpR9ZOwpDjmMotiZCOPu84Guw= 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 6.12 050/242] ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Date: Wed, 8 Apr 2026 20:01:30 +0200 Message-ID: <20260408175928.945211606@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175927.064985309@linuxfoundation.org> References: <20260408175927.064985309@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 6.12-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 e43b49f1ddbb2..387400829b207 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -681,6 +681,9 @@ 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