[PATCH] virtio_net: validate device stats reply records before use
From: Michael Bommarito <hidden>
Date: 2026-07-11 15:07:59
Also in:
lkml, stable, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
__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 <redacted>
---
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