[PATCH 1/1] uas: add stream number sanity checks.

[Gerd Hoffmann]

The device uses the guest-supplied stream number unchecked, which can
lead to guest-triggered out-of-band access to the UASDevice->data3 and
UASDevice->status3 fields.  Add the missing checks.

Fixes: CVE-2021-3713
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/usb/dev-uas.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/hw/usb/dev-uas.c b/hw/usb/dev-uas.c
index 263056231c79..f6309a5ebfdc 100644
--- a/hw/usb/dev-uas.c
+++ b/hw/usb/dev-uas.c
@@ -840,6 +840,9 @@ static void usb_uas_handle_data(USBDevice *dev, USBPacket 
*p)
         }
         break;
     case UAS_PIPE_ID_STATUS:
+        if (p->stream > UAS_MAX_STREAMS) {
+            goto err_stream;
+        }
         if (p->stream) {
             QTAILQ_FOREACH(st, &uas->results, next) {
                 if (st->stream == p->stream) {
@@ -867,6 +870,9 @@ static void usb_uas_handle_data(USBDevice *dev, USBPacket 
*p)
         break;
     case UAS_PIPE_ID_DATA_IN:
     case UAS_PIPE_ID_DATA_OUT:
+        if (p->stream > UAS_MAX_STREAMS) {
+            goto err_stream;
+        }
         if (p->stream) {
             req = usb_uas_find_request(uas, p->stream);
         } else {
@@ -902,6 +908,11 @@ static void usb_uas_handle_data(USBDevice *dev, USBPacket 
*p)
         p->status = USB_RET_STALL;
         break;
     }
+
+err_stream:
+    error_report("%s: invalid stream %d", __func__, p->stream);
+    p->status = USB_RET_STALL;
+    return;
 }
 
 static void usb_uas_unrealize(USBDevice *dev)
-- 
2.31.1