hyperv_receive_sub() reads msg->vid_hdr.type and dispatches into one
of four message-type branches without knowing how many bytes the host
wrote into hv->recv_buf. The completion path then runs
memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that
wakes on wait_for_completion_timeout() can read up to 16 KiB of
residue from a prior message as if it were the response payload.
Pass bytes_recvd into hyperv_receive_sub() and reject any packet that
does not cover the pipe + synthvid header. A single switch on
msg->vid_hdr.type then computes the type-specific payload size: the
three completion-driving types (SYNTHVID_VERSION_RESPONSE,
SYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through
to a shared exit that requires that size before memcpy/complete, while
SYNTHVID_FEATURE_CHANGE validates its own payload and returns before
reading is_dirt_needed. Unknown types are dropped.
SYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills
resolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT
array. Validate the fixed prefix first so resolution_count can be
read, bound it against the array, then require only the count-sized
array, so the shorter responses the host actually sends are accepted.
Only run the sub-handler when vmbus_recvpacket() returned success. The
memcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE
only on a successful receive; on -ENOBUFS vmbus_recvpacket() instead
reports the required length, which can exceed hv->recv_buf, so copying
bytes_recvd would read and write past the 16 KiB buffers. Gating on the
success return keeps the copy bounded. The nonzero-return path is itself
a malformed-message case and is now logged rather than silently skipped;
channel recovery is not attempted.
Rejected packets are reported via drm_err_ratelimited() rather than
silently dropped, matching the CoCo-hardened pattern in
hv_kvp_onchannelcallback().
Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic video
device")
Cc: [email protected] # 5.14+
Signed-off-by: Berkant Koc <[email protected]>
Assisted-by: Claude:claude-opus-4-7 berkoc-pipeline
---
drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 100 +++++++++++++++++++---
1 file changed, 87 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
index c3d0ff229..4e6f703a1 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
@@ -420,30 +420,92 @@ static int hyperv_get_supported_resolution(struct
hv_device *hdev)
return 0;
}
-static void hyperv_receive_sub(struct hv_device *hdev)
+static void hyperv_receive_sub(struct hv_device *hdev, u32 bytes_recvd)
{
struct hyperv_drm_device *hv = hv_get_drvdata(hdev);
struct synthvid_msg *msg;
+ size_t hdr_size;
+ size_t need;
if (!hv)
return;
- msg = (struct synthvid_msg *)hv->recv_buf;
-
- /* Complete the wait event */
- if (msg->vid_hdr.type == SYNTHVID_VERSION_RESPONSE ||
- msg->vid_hdr.type == SYNTHVID_RESOLUTION_RESPONSE ||
- msg->vid_hdr.type == SYNTHVID_VRAM_LOCATION_ACK) {
- memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE);
- complete(&hv->wait);
+ hdr_size = sizeof(struct pipe_msg_hdr) +
+ sizeof(struct synthvid_msg_hdr);
+ if (bytes_recvd < hdr_size) {
+ drm_err_ratelimited(&hv->dev,
+ "synthvid packet too small for header:
%u\n",
+ bytes_recvd);
return;
}
- if (msg->vid_hdr.type == SYNTHVID_FEATURE_CHANGE) {
+ msg = (struct synthvid_msg *)hv->recv_buf;
+ need = hdr_size;
+
+ switch (msg->vid_hdr.type) {
+ case SYNTHVID_VERSION_RESPONSE:
+ need += sizeof(struct synthvid_version_resp);
+ break;
+ case SYNTHVID_RESOLUTION_RESPONSE:
+ /*
+ * The resolution response is variable length: the host
+ * fills resolution_count entries, not the full
+ * SYNTHVID_MAX_RESOLUTION_COUNT array. Require the fixed
+ * prefix first so resolution_count can be read, then
+ * demand exactly the count-sized array.
+ */
+ need += offsetof(struct synthvid_supported_resolution_resp,
+ supported_resolution);
+ if (bytes_recvd < need)
+ break;
+ if (msg->resolution_resp.resolution_count >
+ SYNTHVID_MAX_RESOLUTION_COUNT) {
+ drm_err_ratelimited(&hv->dev,
+ "synthvid resolution count too
large: %u\n",
+
msg->resolution_resp.resolution_count);
+ return;
+ }
+ need += msg->resolution_resp.resolution_count *
+ sizeof(struct hvd_screen_info);
+ break;
+ case SYNTHVID_VRAM_LOCATION_ACK:
+ need += sizeof(struct synthvid_vram_location_ack);
+ break;
+ case SYNTHVID_FEATURE_CHANGE:
+ /*
+ * Not a completion-driving message: validate its own payload
+ * and consume it here rather than falling through to the
+ * memcpy/complete shared by the wait-event responses.
+ */
+ if (bytes_recvd < need +
+ sizeof(struct synthvid_feature_change)) {
+ drm_err_ratelimited(&hv->dev,
+ "synthvid feature change packet too
small: %u\n",
+ bytes_recvd);
+ return;
+ }
hv->dirt_needed = msg->feature_chg.is_dirt_needed;
if (hv->dirt_needed)
hyperv_hide_hw_ptr(hv->hdev);
+ return;
+ default:
+ return;
+ }
+
+ /*
+ * Shared completion path for the wait-event responses
+ * (VERSION_RESPONSE, RESOLUTION_RESPONSE, VRAM_LOCATION_ACK):
+ * require the type-specific payload before handing the buffer to
+ * the waiter.
+ */
+ if (bytes_recvd < need) {
+ drm_err_ratelimited(&hv->dev,
+ "synthvid packet too small for type %u: %u
< %zu\n",
+ msg->vid_hdr.type, bytes_recvd, need);
+ return;
}
+ memcpy(hv->init_buf, msg, bytes_recvd);
+ complete(&hv->wait);
}
static void hyperv_receive(void *ctx)
@@ -464,9 +526,21 @@ static void hyperv_receive(void *ctx)
ret = vmbus_recvpacket(hdev->channel, recv_buf,
VMBUS_MAX_PACKET_SIZE,
&bytes_recvd, &req_id);
- if (bytes_recvd > 0 &&
- recv_buf->pipe_hdr.type == PIPE_MSG_DATA)
- hyperv_receive_sub(hdev);
+ if (ret) {
+ /*
+ * A nonzero return (e.g. -ENOBUFS for an oversized
+ * packet) is itself a malformed message: bytes_recvd
+ * then reports the required length rather than a copied
+ * payload, so it must not be forwarded to the
+ * sub-handler. Channel recovery is not attempted.
+ */
+ drm_err_ratelimited(&hv->dev,
+ "vmbus_recvpacket failed: %d (need
%u)\n",
+ ret, bytes_recvd);
+ } else if (bytes_recvd > 0 &&
+ recv_buf->pipe_hdr.type == PIPE_MSG_DATA) {
+ hyperv_receive_sub(hdev, bytes_recvd);
+ }
} while (bytes_recvd > 0 && ret == 0);
}
--
2.47.3
