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 93F41478E57; Tue, 16 Jun 2026 17:26:58 +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=1781630819; cv=none; b=m8Q6lEytcDefMFBck6IKQiJHXNKDuh/SeZ30CBl14OffkCoOXSMOCePJDNSSwSTV4xBfqHzLJ43vt0PoP1oNvxBLa06V/OQSLoaSFX2ADfwd3ZIKStXazNtbO2UTNlAQOxUYwUFIY9pNbvDiHaEvOA7in1hJDAn8tyqsZPtSsMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781630819; c=relaxed/simple; bh=V0lh+WQqPO5enBAKC/rDPJosp/URTeAiRoVw34iyX9Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ruaOXBD2oMik6OWhIXvzMsVBP6vEn6NG2WSsX95A4QkrQ8S0fbnJLodvwYYbM6+mltE129mJU4gpHoJwXoaw/mOr0OtdNshv57a50ZazD9M0g9EoURTopL8jL8Fpsmo4/4K7kRSyZNcOk9TVa0Bf/Kz2c6Cbbb6qejDGhKL4OlA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=PvZjCwjv; 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="PvZjCwjv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8909C1F00A3A; Tue, 16 Jun 2026 17:26:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781630818; bh=B2Pcqzmm58eNzh/K0cQmSWkw3qiFiCP/x8r6WTQFMco=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PvZjCwjvAiDOblPhtj2HvjT5/J3V0RzMv9AdoLI+/LKzBL7MfLKb0eeKXBZ8rALbj xH0tLJT8KNfjFrHBwOJyuVz2KZ5TTNqYEaFIvjd8zuGmkrLldh8wesnMesREY/PloA iMbWhvcMPAPknPfFQE4omGpsL9SaVEpQlDhnVLaw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bingquan Chen , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 069/522] net/packet: fix TOCTOU race on mmapd vnet_hdr in tpacket_snd() Date: Tue, 16 Jun 2026 20:23:36 +0530 Message-ID: <20260616145129.053927997@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145125.307082728@linuxfoundation.org> References: <20260616145125.307082728@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bingquan Chen [ Upstream commit 2c054e17d9d41f1020376806c7f750834ced4dc5 ] 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: Sasha Levin --- net/packet/af_packet.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 36347814ec7ceb..f3850784d66404 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2767,7 +2767,8 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) { 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; @@ -2868,16 +2869,20 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) hlen = LL_RESERVED_SPACE(dev); tlen = dev->needed_tailroom; if (packet_sock_flag(po, PACKET_SOCK_HAS_VNET_HDR)) { - vnet_hdr = data; - data += sizeof(*vnet_hdr); - tp_len -= sizeof(*vnet_hdr); - if (tp_len < 0 || - __packet_snd_vnet_parse(vnet_hdr, tp_len)) { + data += sizeof(vnet_hdr); + tp_len -= sizeof(vnet_hdr); + if (tp_len < 0) { + tp_len = -EINVAL; + goto tpacket_error; + } + memcpy(&vnet_hdr, data - sizeof(vnet_hdr), 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, @@ -2914,12 +2919,12 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) } } - if (packet_sock_flag(po, PACKET_SOCK_HAS_VNET_HDR)) { - 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; -- 2.53.0