net: ne2000: check ring buffer control registers

Ne2000 NIC uses ring buffer of NE2000_MEM_SIZE(49152)
bytes to process network packets. Registers PSTART & PSTOP
define ring buffer size & location. Setting these registers
to invalid values could lead to infinite loop or OOB r/w
access issues. Add check to avoid it.

Reported-by: Yang Hongke <yanghongke@huawei.com>
Tested-by: Yang Hongke <yanghongke@huawei.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>

diff --git a/hw/net/ne2000.c b/hw/net/ne2000.c
index e408083a58b8ff4b319b612442556361c47d0ae5..f0feaf96b0d8ef3768f7325ad9197205451536d6 100644 (file)
--- a/hw/net/ne2000.c
+++ b/hw/net/ne2000.c
@@ -155,6 +155,10 @@ static int ne2000_buffer_full(NE2000State *s)
 {
     int avail, index, boundary;
 
+    if (s->stop <= s->start) {
+        return 1;
+    }
+
     index = s->curpag << 8;
     boundary = s->boundary << 8;
     if (index < boundary)