[Qemu-devel] [PATCH 2/2] cadence_gem: avoid stack-writing buffer-overrun

[Jim Meyering <jim@meyering.net>]

From: Jim Meyering <meyering@redhat.com>

Use sizeof(rxbuf)-size (not sizeof(rxbuf-size)) as the number
of bytes to clear.  The latter would always clear 4 or 8
bytes, possibly writing beyond the end of that stack buffer.
Alternatively, depending on the value of the "size" parameter,
it could fail to initialize the end of "rxbuf".
Spotted by coverity.

Signed-off-by: Jim Meyering <meyering@redhat.com>
---
 hw/cadence_gem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/cadence_gem.c b/hw/cadence_gem.c
index e2140ae..dbde392 100644
--- a/hw/cadence_gem.c
+++ b/hw/cadence_gem.c
@@ -664,7 +664,7 @@ static ssize_t gem_receive(VLANClientState *nc, const uint8_t *buf, size_t size)
          */

         memcpy(rxbuf, buf, size);
-        memset(rxbuf + size, 0, sizeof(rxbuf - size));
+        memset(rxbuf + size, 0, sizeof(rxbuf) - size);
         rxbuf_ptr = rxbuf;
         crc_val = cpu_to_le32(crc32(0, rxbuf, MAX(size, 60)));
         if (size < 60) {
-- 
1.7.10.1.487.ga3935e6