[Qemu-devel] [PATCH 1/2] usb: check RNDIS message length

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

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>
---
 hw/usb/core.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

Update as per review
  -> https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg03475.html

diff --git a/hw/usb/core.c b/hw/usb/core.c
index d0025db..7f46370 100644
--- a/hw/usb/core.c
+++ b/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)) {
-- 
2.5.0