[Qemu-devel] [PATCH 3/4] pcnet: fix Negative array index read

[arei.gonglei]

From: Gonglei <address@hidden>

s->xmit_pos maybe assigned to a negative value (-1),
but in this branch variable s->xmit_pos as an index to
array s->buffer. Let's add a check for s->xmit_pos.

Signed-off-by: Gonglei <address@hidden>
---
 hw/net/pcnet.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index d344c15..2bb6417 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -1247,7 +1247,7 @@ static void pcnet_transmit(PCNetState *s)
             s->xmit_pos = -1;
             goto txdone;
         }
-        if (!GET_FIELD(tmd.status, TMDS, ENP)) {
+        if (!GET_FIELD(tmd.status, TMDS, ENP) && (s->xmit_pos >= 0)) {
             int bcnt = 4096 - GET_FIELD(tmd.length, TMDL, BCNT);
             s->phys_mem_read(s->dma_opaque, PHYSADDR(s, tmd.tbadr),
                              s->buffer + s->xmit_pos, bcnt, CSR_BSWP(s));
-- 
1.7.12.4