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[68.48.65.54]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8ffd57baf8dsm69025296d6.20.2026.07.11.08.07.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Jul 2026 08:07:58 -0700 (PDT) From: Michael Bommarito To: "Michael S . Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?q?P=C3=A9rez?= Cc: Andrew Lunn , Jakub Kicinski , Paolo Abeni , virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] virtio_net: validate device stats reply records before use Date: Sat, 11 Jul 2026 11:07:54 -0400 Message-ID: <20260711150754.2918392-1-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit __virtnet_get_hw_stats() walks the device statistics reply buffer with "for (p = reply; p - reply < res_size; p += le16_to_cpu(hdr->size))", using each record's device-supplied hdr->size as the stride without checking that a full struct virtio_net_stats_reply_hdr remains, that hdr->size is nonzero and matches the expected size for hdr->type, or that the record fits within res_size. A backend that returns hdr->size == 0 spins the loop forever; a short or oversized size drives out-of-bounds reads in virtnet_fill_stats(). Impact: a malicious or compromised virtio-net backend hangs the CPU running the guest's device-statistics query in an infinite loop (hdr->size == 0), or drives an out-of-bounds read of the reply buffer. This matters most for a confidential guest, where the host is outside the trust boundary. Validate each record before use: require a full header in the remaining bytes, a nonzero hdr->size that is at least the header size and matches the size expected for hdr->type, and that the record fits within res_size; stop the walk otherwise. Add virtnet_stats_reply_size() for the per-type size. Fixes: 941168f8b40e ("virtio_net: support device stats") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito --- drivers/net/virtio_net.c | 42 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 40 insertions(+), 2 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 3e2a5876c6c8c..9cbe40d218cc4 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3532,6 +3532,7 @@ static int virtnet_tx_resize(struct virtnet_info *vi, struct send_queue *sq, return err; } + /* * Send command via the control virtqueue and check status. Commands * supported by the hypervisor, as indicated by feature bits, should @@ -3546,6 +3547,7 @@ static bool virtnet_send_command_reply(struct virtnet_info *vi, u8 class, u8 cmd bool ok; int ret; + /* Caller should know better */ BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)); @@ -4927,6 +4929,32 @@ static void virtnet_fill_stats(struct virtnet_info *vi, u32 qid, } } +static int virtnet_stats_reply_size(u8 type) +{ + switch (type) { + case VIRTIO_NET_STATS_TYPE_REPLY_CVQ: + return sizeof(struct virtio_net_stats_cvq); + case VIRTIO_NET_STATS_TYPE_REPLY_RX_BASIC: + return sizeof(struct virtio_net_stats_rx_basic); + case VIRTIO_NET_STATS_TYPE_REPLY_RX_CSUM: + return sizeof(struct virtio_net_stats_rx_csum); + case VIRTIO_NET_STATS_TYPE_REPLY_RX_GSO: + return sizeof(struct virtio_net_stats_rx_gso); + case VIRTIO_NET_STATS_TYPE_REPLY_RX_SPEED: + return sizeof(struct virtio_net_stats_rx_speed); + case VIRTIO_NET_STATS_TYPE_REPLY_TX_BASIC: + return sizeof(struct virtio_net_stats_tx_basic); + case VIRTIO_NET_STATS_TYPE_REPLY_TX_CSUM: + return sizeof(struct virtio_net_stats_tx_csum); + case VIRTIO_NET_STATS_TYPE_REPLY_TX_GSO: + return sizeof(struct virtio_net_stats_tx_gso); + case VIRTIO_NET_STATS_TYPE_REPLY_TX_SPEED: + return sizeof(struct virtio_net_stats_tx_speed); + default: + return sizeof(struct virtio_net_stats_reply_hdr); + } +} + static int __virtnet_get_hw_stats(struct virtnet_info *vi, struct virtnet_stats_ctx *ctx, struct virtio_net_ctrl_queue_stats *req, @@ -4936,7 +4964,7 @@ static int __virtnet_get_hw_stats(struct virtnet_info *vi, struct scatterlist sgs_in, sgs_out; void *p; u32 qid; - int ok; + int hdr_size, ok, remaining; sg_init_one(&sgs_out, req, req_size); sg_init_one(&sgs_in, reply, res_size); @@ -4948,8 +4976,17 @@ static int __virtnet_get_hw_stats(struct virtnet_info *vi, if (!ok) return ok; - for (p = reply; p - reply < res_size; p += le16_to_cpu(hdr->size)) { + for (p = reply; p - reply < res_size; p += hdr_size) { + remaining = res_size - (p - reply); + if (remaining < sizeof(*hdr)) + return -EINVAL; + hdr = p; + hdr_size = le16_to_cpu(hdr->size); + if (hdr_size < virtnet_stats_reply_size(hdr->type) || + hdr_size > remaining) + return -EINVAL; + qid = le16_to_cpu(hdr->vq_index); virtnet_fill_stats(vi, qid, ctx, p, false, hdr->type); } @@ -7305,3 +7342,4 @@ module_exit(virtio_net_driver_exit); MODULE_DEVICE_TABLE(virtio, id_table); MODULE_DESCRIPTION("Virtio network driver"); MODULE_LICENSE("GPL"); + -- 2.53.0