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From: Jason Wang <jasowang@redhat.com>
Date: Mon, 30 Nov 2015 15:00:06 +0800
Subject: [PATCH] pcnet: fix rx buffer overflow(CVE-2015-7512)

Backends could provide a packet whose length is greater than buffer
size. Check for this and truncate the packet to avoid rx buffer
overflow in this case.

Cc: Prasad J Pandit <pjp@fedoraproject.org>
Cc: qemu-stable@nongnu.org
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit 8b98a2f07175d46c3f7217639bd5e03f2ec56343)
---
 hw/net/pcnet.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index 03a56b2..d8957ab 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -1074,6 +1074,12 @@ ssize_t pcnet_receive(NetClientState *nc, const uint8_t *buf, size_t size_)
             int pktcount = 0;
 
             if (!s->looptest) {
+                if (size > 4092) {
+#ifdef PCNET_DEBUG_RMD
+                    fprintf(stderr, "pcnet: truncates rx packet.\n");
+#endif
+                    size = 4092;
+                }
                 memcpy(src, buf, size);
                 /* no need to compute the CRC */
                 src[size] = 0;