net: avoid infinite loop when receiving packets(CVE-2015-5278)

Ne2000 NIC uses ring buffer of NE2000_MEM_SIZE(49152)
bytes to process network packets. While receiving packets
via ne2000_receive() routine, a local 'index' variable
could exceed the ring buffer size, leading to an infinite
loop situation.

Reported-by: Qinghao Tang <luodalongde@gmail.com>
Signed-off-by: P J P <pjp@fedoraproject.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 737d2b3c41d59eb8f94ab7eb419b957938f24943)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/net/ne2000.c b/hw/net/ne2000.c
index 9278571..2bdb4c9 100644 (file)
--- a/hw/net/ne2000.c
+++ b/hw/net/ne2000.c
@@ -256,7 +256,7 @@ ssize_t ne2000_receive(NetClientState *nc, const uint8_t *buf, size_t size_)
         if (index <= s->stop)
             avail = s->stop - index;
         else
-            avail = 0;
+            break;
         len = size;
         if (len > avail)
             len = avail;