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 6C8B7442118; Tue, 21 Jul 2026 22:18:32 +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=1784672313; cv=none; b=mRA/+vdpFEqNPtV95BuXdCo1KVNXOalphMVLL5DFqiVZAhW6tjT4aYqotzywNzROFTTxEhhd1wZ879cntDxa3pcZPUhZ0xVNnR3h4poPaz23743lR3prOGPz80mO1YC6f+O4GYauFqNFqCp+iJ/HDgBFqLjZUE7qbEf/RQlKqw8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784672313; c=relaxed/simple; bh=v1mY1RbhdH/0jx6+XBNBtvg80eQox0pL4a65Rz+SkSM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WF3fMirckYvHZRy2AGbNTAmU8+bRSldY8xJlK/7AHCwAk3PLaKrg5+RwzKb9FsuAaYemPxgd3Oop8xiCQebz9B/H4bw8BpgozI+xItmm5+tTQcSiEds56yAXthTpYvGFsdL1dWP65D2oZPfOHstsWvLVIzQCmJKpognF7bnop/w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sBck1ukM; 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="sBck1ukM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7EE311F000E9; Tue, 21 Jul 2026 22:18:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784672312; bh=NC1tbsUPKRSIx/kO5mjFvhRVVkiis4LZXr53yUzE1bc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=sBck1ukM4VR3gNSEKQmlYVi0XGYAl8xYNFdm4r3IMyAZr7dCbmUt+2M4gYq41gqTH VhcMoe5qfx4+ALmjRpsS4C1qbSduL7X/1oK8S7LGOsUqQGK6ztObJU3diBhGl51grm tbfWFUMPtZ9Yc/DrrVaivHORkqmpqVkKxbtDwkTI= 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 5.15 576/843] netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag Date: Tue, 21 Jul 2026 17:23:31 +0200 Message-ID: <20260721152419.006307317@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152405.946368001@linuxfoundation.org> References: <20260721152405.946368001@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 5.15-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 @@ -345,7 +345,8 @@ 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);