__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: [email protected]
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito <[email protected]>
---
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
