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 30FE430EF7E; Tue, 21 Jul 2026 19:52:27 +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=1784663548; cv=none; b=nhZSQXBfiSV15onJWFe4v1+a48U/BB1/KGso80UGXfkLlPtG6jKCtI9BcrSebyf1e6cpq+MiwDhANTrKhWnp6RRFT0EseTcmIhrQfA5F/iwWTUT430sV4JrRBb+4DuzFZ+tpIfI5RDfcURAkSdV4do99b9WOUnlX0S3WoxNrX28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784663548; c=relaxed/simple; bh=Oil2O5aqkxqC1wS5rinXicm+8Ogl6NyQodpz9pL370g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DemTx8YfDGnDkJjwbLPzs9rbtyWAGEkZeTDFrwbDtvIOz39q6Vu6PKhbc7q/DBB5MT/NCK1Ca2sdViKp9ElXdzLcduvBZwdwalJ7lVvm0RcMN9OMTdCE0rGa5a4OTmJA/S4MWTHOlxPYxvukxcHrVeV+KLnHOyblpGIv5sNKpgw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lJV1f7Si; 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="lJV1f7Si" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 91F471F000E9; Tue, 21 Jul 2026 19:52:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784663547; bh=+4XMYJ4Zfv/FM3qXZs6SrOx2FXX4UCq0KwqEmy9bH4I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lJV1f7SiCBaulyjKN2PL6Scv2yqczOIrSQ9/Kuw3497l3+9sJGpWG/vHlw3IlRDyy E07szH48fThbxVYL4QPupeJvA+nHA9jejmuyoHRKKHn9h4fTVZv1Xq6nnVovv9Rue4 QnTuFxjso4Ch1S+i9VLSc3IdIvE/q7x22sxX2ip4= 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 6.12 0863/1276] netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag Date: Tue, 21 Jul 2026 17:21:46 +0200 Message-ID: <20260721152505.364282216@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@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 6.12-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);