[Qemu-devel] [PATCH 1/6] rtl8139: limit transmission buffer size in c+ mode

[Jason Wang]

The tx buffer would be re-allocated for tx descriptor with big size
and without LS bit set, this would make guest driver could easily let
qemu to allocate unlimited.

In linux host, a glib failure were easy to be triggered:

GLib-ERROR **: gmem.c:176: failed to allocate 18446744071562067968 bytes

This patch fix this by adding a limit. As the spec didn't tell the maximum size
of buffer allowed, stick it to  current CP_TX_BUFFER_SIZE (65536).

Signed-off-by: Jason Wang <address@hidden>
---
 hw/rtl8139.c |    9 ++++-----
 1 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index 05b8e1e..d9e742c 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -2063,11 +2063,10 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
 
     while (s->cplus_txbuffer && s->cplus_txbuffer_offset + txsize >= 
s->cplus_txbuffer_len)
     {
-        s->cplus_txbuffer_len += CP_TX_BUFFER_SIZE;
-        s->cplus_txbuffer = g_realloc(s->cplus_txbuffer, 
s->cplus_txbuffer_len);
-
-        DPRINTF("+++ C+ mode transmission buffer space changed to %d\n",
-            s->cplus_txbuffer_len);
+        /* The spec didn't tell the maximum size, stick to CP_TX_BUFFER_SIZE */
+        txsize = s->cplus_txbuffer_len - s->cplus_txbuffer_offset;
+        DPRINTF("+++ C+ mode transmission buffer overrun, truncated descriptor"
+                "length to %d\n", txsize);
     }
 
     if (!s->cplus_txbuffer)