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 726863D47AC; Wed, 8 Apr 2026 18:28:58 +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=1775672938; cv=none; b=UzKg4WAb8iAVFoWSWbTDPBgwK/jI+JKWY5c0LW2ZqzkPXpIfUbXpaqOTng0q2mcEH7tR7b5eX4+SOX63JwYWWg3HvzpBmPc0b2bFSkYZFwe0ER39WeBqZTh4fMBb84KnIMFb1iJW6XlKCL8AxXcb2P+kjNmD9B65nrtW9iVrrSY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775672938; c=relaxed/simple; bh=8Xc1mJTZ5Dx1GYvf78nRoE22J/GIyKwjLRu59uURHvA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ng7oQOGh7iWC2brnmNWizrEOhYJDEOWWWedbKDdCP71rWha0qhxr27LCa9JkYB3Uz5SaApxbVgCOzRSemloLIH1M5f00PhRW1JtozDGCNgyzHLdE5Pk9YyW2wgku5TcvWzNg3vIYPMXh7qgF9RITlAXWCjoEp7cHFYQKbrTuowg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BXHi+0ut; 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="BXHi+0ut" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08C60C2BC87; Wed, 8 Apr 2026 18:28:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775672938; bh=8Xc1mJTZ5Dx1GYvf78nRoE22J/GIyKwjLRu59uURHvA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BXHi+0utWfCmkY3gjXYtzu0xxKze9Ec3+cfX/ESTYH/PAK5gx6usT6+qH65XTUOHn a9uACfAiaWFuJegTrn4NiYQxF69xEDN00kWyWDQi/KkZ6RGGM1M0Urjn79X0ehdK3Z yB/qZODZobVUfkurAM/tI71vwHYp+iBMHbk6RE4A= 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 6.18 037/277] ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Date: Wed, 8 Apr 2026 20:00:22 +0200 Message-ID: <20260408175935.239369689@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175933.836769063@linuxfoundation.org> References: <20260408175933.836769063@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 6.18-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 54ad4c7578679..aa39aabe4417e 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -675,6 +675,9 @@ 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