[Qemu-devel] [PATCH v3] net: stellaris_enet: check packet length against receive buffer

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

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

When receiving packets over Stellaris ethernet controller, it
uses receive buffer of size 2048 bytes. In case the controller
accepts large(MTU) packets, it could lead to memory corruption.
Add check to avoid it.

Reported-by: Oleksandr Bazhaniuk <oleksandr.bazhaniuk@intel.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/net/stellaris_enet.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Update per review:
  -> https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01173.html

diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
index 21a4773..fc48ba8 100644
--- a/hw/net/stellaris_enet.c
+++ b/hw/net/stellaris_enet.c
@@ -235,8 +235,18 @@ static ssize_t stellaris_enet_receive(NetClientState *nc, const uint8_t *buf, si
     n = s->next_packet + s->np;
     if (n >= 31)
         n -= 31;
+
+    if (size >= sizeof(s->rx[n].data) - 6) {
+        /* If the packet won't fit into the
+         * emulated 2K RAM, this is reported
+         * as a FIFO overrun error.
+         */
+        s->ris |= SE_INT_FOV;
+        stellaris_enet_update(s);
+        return -1;
+    }
+
     s->np++;
-
     s->rx[n].len = size + 6;
     p = s->rx[n].data;
     *(p++) = (size + 6);
-- 
2.5.5