[Qemu-devel] [PATCH v2] net: ne2000: check ring buffer control registers

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

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

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>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/net/ne2000.c | 4 ++++
 1 file changed, 4 insertions(+)

Update per review:
  -> https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg05522.html

diff --git a/hw/net/ne2000.c b/hw/net/ne2000.c
index b032212..ced4666 100644
--- a/hw/net/ne2000.c
+++ b/hw/net/ne2000.c
@@ -154,6 +154,10 @@ 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)
-- 
2.5.0