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 793BD3D75C2; Fri, 24 Apr 2026 13:44:24 +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=1777038264; cv=none; b=Vh6OS5ytiXS1W0KgdS1isd7zX6dWlyjq+UGJXKGhuUdePhhEv3xncwpycLXxdj7OJDGlziYKATq0rdKgvi5R30vbHRs2ES786xNoAaU/ppxlv8k7DHYPVZYKOlgcqGYlpiKpVbQ19Ja3QMwdYgQM1jqKO86ZryxCR0E93W144eg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777038264; c=relaxed/simple; bh=XmDkEOHwjdYBLAEMKq7rbPG0JoTZmV0pqeISfyUrd2c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fw99ZYGpYXmFV/e4HGoWFTxP3WTpgAI1oIOAufrFEONtWXq7NhbiWSPEB4BMgcNNST7qr4PconOzXBiOFhu1ZU3HXQaPOVL/cyH8+7epq6FuvALpVYjg6Wb+puwXknea2MQhbwwfKMWtM62Sic8ekSgfe5us2+vFTOTLj4We2TA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gfj5xCyF; 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="gfj5xCyF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6A60C19425; Fri, 24 Apr 2026 13:44:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777038264; bh=XmDkEOHwjdYBLAEMKq7rbPG0JoTZmV0pqeISfyUrd2c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gfj5xCyFHxi/dra1nGDE+XLPbJ5+SHZpwwj+3Haauf1prNQflgzgCWsXS2debS6mM TBA1b/tob9oC1nR7c7NMOEKXk538l8gQ0OCOW27xoRzN0FUIJVuKp6OpVroYod7yO1 GD8uxX3JvfBtKpA7q6jF47qWhdhCMlNu0lSY5v+U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bingquan Chen , Willem de Bruijn , Jakub Kicinski Subject: [PATCH 6.12 31/35] net/packet: fix TOCTOU race on mmapd vnet_hdr in tpacket_snd() Date: Fri, 24 Apr 2026 15:31:38 +0200 Message-ID: <20260424132418.323892323@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260424132411.427029259@linuxfoundation.org> References: <20260424132411.427029259@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: Bingquan Chen commit 2c054e17d9d41f1020376806c7f750834ced4dc5 upstream. In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points directly into the mmap'd TX ring buffer shared with userspace. The kernel validates the header via __packet_snd_vnet_parse() but then re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent userspace thread can modify the vnet_hdr fields between validation and use, bypassing all safety checks. The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr to a stack-local variable. All other vnet_hdr consumers in the kernel (tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX path is the only caller of virtio_net_hdr_to_skb() that reads directly from user-controlled shared memory. Fix this by copying vnet_hdr from the mmap'd ring buffer to a stack-local variable before validation and use, consistent with the approach used in packet_snd() and all other callers. Fixes: 1d036d25e560 ("packet: tpacket_snd gso and checksum offload") Signed-off-by: Bingquan Chen Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260418112006.78823-1-patzilla007@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/packet/af_packet.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2770,7 +2770,8 @@ static int tpacket_snd(struct packet_soc { struct sk_buff *skb = NULL; struct net_device *dev; - struct virtio_net_hdr *vnet_hdr = NULL; + struct virtio_net_hdr vnet_hdr; + bool has_vnet_hdr = false; struct sockcm_cookie sockc; __be16 proto; int err, reserve = 0; @@ -2871,16 +2872,20 @@ static int tpacket_snd(struct packet_soc hlen = LL_RESERVED_SPACE(dev); tlen = dev->needed_tailroom; if (vnet_hdr_sz) { - vnet_hdr = data; data += vnet_hdr_sz; tp_len -= vnet_hdr_sz; - if (tp_len < 0 || - __packet_snd_vnet_parse(vnet_hdr, tp_len)) { + if (tp_len < 0) { + tp_len = -EINVAL; + goto tpacket_error; + } + memcpy(&vnet_hdr, data - vnet_hdr_sz, sizeof(vnet_hdr)); + if (__packet_snd_vnet_parse(&vnet_hdr, tp_len)) { tp_len = -EINVAL; goto tpacket_error; } copylen = __virtio16_to_cpu(vio_le(), - vnet_hdr->hdr_len); + vnet_hdr.hdr_len); + has_vnet_hdr = true; } copylen = max_t(int, copylen, dev->hard_header_len); skb = sock_alloc_send_skb(&po->sk, @@ -2917,12 +2922,12 @@ tpacket_error: } } - if (vnet_hdr_sz) { - if (virtio_net_hdr_to_skb(skb, vnet_hdr, vio_le())) { + if (has_vnet_hdr) { + if (virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le())) { tp_len = -EINVAL; goto tpacket_error; } - virtio_net_hdr_set_proto(skb, vnet_hdr); + virtio_net_hdr_set_proto(skb, &vnet_hdr); } skb->destructor = tpacket_destruct_skb;