[PATCH] hw/net/xgmac: Fix buffer overflow in xgmac_enet_send()

[Mauro Matteo Cascella <mcascell@redhat.com>]

A buffer overflow issue was reported by Mr. Ziming Zhang, CC'd here. It
occurs while sending an Ethernet frame due to missing break statements
and improper checking of the buffer size.

Reported-by: Ziming Zhang <ezrakiez@gmail.com>
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
---
 hw/net/xgmac.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/hw/net/xgmac.c b/hw/net/xgmac.c
index 574dd47b41..b872afbb1a 100644
--- a/hw/net/xgmac.c
+++ b/hw/net/xgmac.c
@@ -224,17 +224,20 @@ static void xgmac_enet_send(XgmacState *s)
             DEBUGF_BRK("qemu:%s:ERROR...ERROR...ERROR... -- "
                         "xgmac buffer 1 len on send > 2048 (0x%x)\n",
                          __func__, bd.buffer1_size & 0xfff);
+            break;
         }
         if ((bd.buffer2_size & 0xfff) != 0) {
             DEBUGF_BRK("qemu:%s:ERROR...ERROR...ERROR... -- "
                         "xgmac buffer 2 len on send != 0 (0x%x)\n",
                         __func__, bd.buffer2_size & 0xfff);
+            break;
         }
-        if (len >= sizeof(frame)) {
+        if (frame_size + len >= sizeof(frame)) {
             DEBUGF_BRK("qemu:%s: buffer overflow %d read into %zu "
-                        "buffer\n" , __func__, len, sizeof(frame));
+                        "buffer\n" , __func__, frame_size + len, sizeof(frame));
             DEBUGF_BRK("qemu:%s: buffer1.size=%d; buffer2.size=%d\n",
                         __func__, bd.buffer1_size, bd.buffer2_size);
+            break;
         }
 
         cpu_physical_memory_read(bd.buffer1_addr, ptr, len);
-- 
2.26.2