ne2000: fix possible out of bound access in ne2000_receive

In ne2000_receive(), we try to assign size_ to size which converts
from size_t to integer. This will cause troubles when size_ is greater
INT_MAX, this will lead a negative value in size and it can then pass
the check of size < MIN_BUF_SIZE which may lead out of bound access of
for both buf and buf1.

Fixing by converting the type of size to size_t.

CC: qemu-stable@nongnu.org
Reported-by: Daniel Shapira <daniel@twistlock.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/ne2000.c

@@ -174,15 +174,15 @@ static int ne2000_buffer_full(NE2000State *s)
 ssize_t ne2000_receive(NetClientState *nc, const uint8_t *buf, size_t size_)
 {
     NE2000State *s = qemu_get_nic_opaque(nc);
-    int size = size_;
+    size_t size = size_;
     uint8_t *p;
     unsigned int total_len, next, avail, len, index, mcast_idx;
     uint8_t buf1[60];
     static const uint8_t broadcast_macaddr[6] =
         { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 
 #if defined(DEBUG_NE2000)
-    printf("NE2000: received len=%d\n", size);
+    printf("NE2000: received len=%zu\n", size);
 #endif
 
     if (s->cmd & E8390_STOP || ne2000_buffer_full(s))