usb: check RNDIS message length

When processing remote NDIS control message packets, the USB Net
device emulator uses a fixed length(4096) data buffer. The incoming
packet length could exceed this limit. Add a check to avoid it.

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-id: 1455648821-17340-2-git-send-email-ppandit@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 64c9bc1)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/usb/core.c

@@ -128,9 +128,16 @@ static void do_token_setup(USBDevice *s, USBPacket *p)
     }
 
     usb_packet_copy(p, s->setup_buf, p->iov.size);
+    s->setup_index = 0;
     p->actual_length = 0;
     s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
-    s->setup_index = 0;
+    if (s->setup_len > sizeof(s->data_buf)) {
+        fprintf(stderr,
+                "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
+                s->setup_len, sizeof(s->data_buf));
+        p->status = USB_RET_STALL;
+        return;
+    }
 
     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
@@ -151,13 +158,6 @@ static void do_token_setup(USBDevice *s, USBPacket *p)
         }
         s->setup_state = SETUP_STATE_DATA;
     } else {
-        if (s->setup_len > sizeof(s->data_buf)) {
-            fprintf(stderr,
-                "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
-                s->setup_len, sizeof(s->data_buf));
-            p->status = USB_RET_STALL;
-            return;
-        }
         if (s->setup_len == 0)
             s->setup_state = SETUP_STATE_ACK;
         else
@@ -176,7 +176,7 @@ static void do_token_in(USBDevice *s, USBPacket *p)
     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
     index   = (s->setup_buf[5] << 8) | s->setup_buf[4];
- 
+
     switch(s->setup_state) {
     case SETUP_STATE_ACK:
         if (!(s->setup_buf[0] & USB_DIR_IN)) {