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 6300544AB91; Tue, 21 Jul 2026 22:49:57 +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=1784674198; cv=none; b=eTzQ/haa+fsyAIA4S4GUkt5XLcKxvvoD5HtCE8D4nMq5R82/OQayWk6Ur+RfZ55TSW4PkqpHpZ0UZzGNtbD51GJKg8IsoTKEjPjFEH7878ijUoNxSVt9NDtKZolUe+pDpvInz1lLarv80v5GfyG5hhROgXiPIjLNBaRNG3CakUI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784674198; c=relaxed/simple; bh=kwUwU3O+H2RjUnmVzBOtz2p/ZMYQ+z+T8O2IqJRTC/0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZcGmK2Rus3PJ3Y6jI9IlLHfBZ9FLl1gLbAzloawip0Ec+/YeSo7jORajjaDCqSfOFitYfUXt5llqFbOJDUmCeFFf7x4W1gtwc3G4odgahGrhEXhVNEmytJblsACmvMBEnYFNiGOgpPEeQ22tJ/HN0qzWLcbYAVBNbQXQ52Z9g+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ACBYCJkt; 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="ACBYCJkt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A85DE1F00A3A; Tue, 21 Jul 2026 22:49:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784674197; bh=BxPxfnDelFNLzwipJlUU+fQOZWJeRn3/oZWV5io2tZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ACBYCJktW1lmz6jiQg22XrxhCL0A4QWhkUxK5Bo4M00IfuIYOUoKlcNt5w0fInN2Z 6pHJ0g/XKexqTUlHCC+raSMUwaht0shGgH8cITFRX6ENKEY8rzQ9HThD3gd534tYQu vRc3KpC+4R2AUPZgyax508RW23A//lprlXFTO/u8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Weiming Shi , Xiang Mei , Florian Westphal Subject: [PATCH 5.10 448/699] netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag Date: Tue, 21 Jul 2026 17:23:27 +0200 Message-ID: <20260721152405.805754925@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152355.667394603@linuxfoundation.org> References: <20260721152355.667394603@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: Xiang Mei commit 3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9 upstream. nf_ct_frag6_reasm() slides the packet head forward to drop the IPv6 fragment header and then unconditionally advances skb->mac_header: skb->mac_header += sizeof(struct frag_hdr); On the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header yet, so skb->mac_header is still the "not set" sentinel (u16)~0U. Adding sizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7), after which skb_mac_header_was_set() wrongly reports a MAC header is present and skb_mac_header() points into the headroom. The reassembler has done this unconditional add since it was introduced; it was harmless while mac_header was a bare pointer, but wrong once mac_header became a u16 offset whose unset state is the ~0U sentinel tested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c does the same relocation and does guard the adjustment; mirror the guard here. Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.") Cc: stable@vger.kernel.org Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Signed-off-by: Florian Westphal Signed-off-by: Greg Kroah-Hartman --- net/ipv6/netfilter/nf_conntrack_reasm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -344,7 +344,8 @@ static int nf_ct_frag6_reasm(struct frag skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0]; memmove(skb->head + sizeof(struct frag_hdr), skb->head, (skb->data - skb->head) - sizeof(struct frag_hdr)); - skb->mac_header += sizeof(struct frag_hdr); + if (skb_mac_header_was_set(skb)) + skb->mac_header += sizeof(struct frag_hdr); skb->network_header += sizeof(struct frag_hdr); skb_reset_transport_header(skb);