The Hyper-V synthetic HID host supplies SYNTH_HID_INITIAL_DEVICE_INFO
messages that contain a HID descriptor followed by the report descriptor
bytes. mousevsc_on_receive_device_info() trusts bLength and
wDescriptorLength without checking that the received packet contains both
byte ranges.
A malformed host or backend message can therefore make the guest read
past the received VMBus packet while copying the report descriptor. Pass
the received initial-device-info size into the parser and reject
descriptor lengths that exceed the packet.
Impact: A malicious Hyper-V host or backend can crash a guest by sending
a short initial device-info message with an oversized HID report
descriptor length.
Fixes: b95f5bcb811e ("HID: Move the hid-hyperv driver out of staging")
Cc: [email protected]
Assisted-by: Codex:gpt-5-5-xhigh
Signed-off-by: Michael Bommarito <[email protected]>
---
drivers/hid/hid-hyperv.c | 27 ++++++++++++++++++++++++---
1 file changed, 24 insertions(+), 3 deletions(-)
diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c
index 7d2b0063df151..fd90196430e29 100644
--- a/drivers/hid/hid-hyperv.c
+++ b/drivers/hid/hid-hyperv.c
@@ -171,18 +171,32 @@ static void mousevsc_free_device(struct mousevsc_dev
*device)
}
static void mousevsc_on_receive_device_info(struct mousevsc_dev *input_device,
- struct synthhid_device_info *device_info)
+ struct synthhid_device_info
*device_info,
+ u32 device_info_size)
{
int ret = 0;
struct hid_descriptor *desc;
struct mousevsc_prt_msg ack;
+ size_t desc_offset;
+ size_t desc_size;
input_device->dev_info_status = -ENOMEM;
+ if (device_info_size < sizeof(*device_info)) {
+ input_device->dev_info_status = -EINVAL;
+ goto cleanup;
+ }
+
input_device->hid_dev_info = device_info->hid_dev_info;
desc = &device_info->hid_descriptor;
+ desc_offset = offsetof(struct synthhid_device_info, hid_descriptor);
+ desc_size = device_info_size - desc_offset;
if (desc->bLength == 0)
goto cleanup;
+ if (desc->bLength < sizeof(*desc) || desc->bLength > desc_size) {
+ input_device->dev_info_status = -EINVAL;
+ goto cleanup;
+ }
/* The pointer is not NULL when we resume from hibernation */
kfree(input_device->hid_desc);
@@ -197,6 +211,10 @@ static void mousevsc_on_receive_device_info(struct
mousevsc_dev *input_device,
input_device->dev_info_status = -EINVAL;
goto cleanup;
}
+ if (input_device->report_desc_size > desc_size - desc->bLength) {
+ input_device->dev_info_status = -EINVAL;
+ goto cleanup;
+ }
/* The pointer is not NULL when we resume from hibernation */
kfree(input_device->report_desc);
@@ -273,14 +291,17 @@ static void mousevsc_on_receive(struct hv_device *device,
break;
case SYNTH_HID_INITIAL_DEVICE_INFO:
- WARN_ON(pipe_msg->size < sizeof(struct hv_input_dev_info));
+ if (WARN_ON_ONCE(pipe_msg->size <
+ sizeof(struct synthhid_device_info)))
+ break;
/*
* Parse out the device info into device attr,
* hid desc and report desc
*/
mousevsc_on_receive_device_info(input_dev,
- (struct synthhid_device_info *)pipe_msg->data);
+ (struct synthhid_device_info
*)pipe_msg->data,
+ pipe_msg->size);
break;
case SYNTH_HID_INPUT_REPORT:
input_report =
--
2.53.0
