[Qemu-devel] [PATCH 2/2] usb: check RNDIS buffer offsets & 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 informationBufferOffset & Length combination could
overflow and cross that range. Check control message buffer
offsets and length to avoid it.

Reported-by: Qinghao Tang <luodalongde@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/usb/dev-network.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

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

diff --git a/hw/usb/dev-network.c b/hw/usb/dev-network.c
index 8a4ff49..180adce 100644
--- a/hw/usb/dev-network.c
+++ b/hw/usb/dev-network.c
@@ -915,8 +915,9 @@ static int rndis_query_response(USBNetState *s,
 
     bufoffs = le32_to_cpu(buf->InformationBufferOffset) + 8;
     buflen = le32_to_cpu(buf->InformationBufferLength);
-    if (bufoffs + buflen > length)
+    if (buflen > length || bufoffs >= length || bufoffs + buflen > length) {
         return USB_RET_STALL;
+    }
 
     infobuflen = ndis_query(s, le32_to_cpu(buf->OID),
                             bufoffs + (uint8_t *) buf, buflen, infobuf,
@@ -961,8 +962,9 @@ static int rndis_set_response(USBNetState *s,
 
     bufoffs = le32_to_cpu(buf->InformationBufferOffset) + 8;
     buflen = le32_to_cpu(buf->InformationBufferLength);
-    if (bufoffs + buflen > length)
+    if (buflen > length || bufoffs >= length || bufoffs + buflen > length) {
         return USB_RET_STALL;
+    }
 
     ret = ndis_set(s, le32_to_cpu(buf->OID),
                     bufoffs + (uint8_t *) buf, buflen);
@@ -1212,8 +1214,9 @@ static void usb_net_handle_dataout(USBNetState *s, USBPacket *p)
     if (le32_to_cpu(msg->MessageType) == RNDIS_PACKET_MSG) {
         uint32_t offs = 8 + le32_to_cpu(msg->DataOffset);
         uint32_t size = le32_to_cpu(msg->DataLength);
-        if (offs + size <= len)
+        if (offs < len && size < len && offs + size <= len) {
             qemu_send_packet(qemu_get_queue(s->nic), s->out_buf + offs, size);
+        }
     }
     s->out_ptr -= len;
     memmove(s->out_buf, &s->out_buf[len], s->out_ptr);
-- 
2.5.0