[PATCH 4.9 09/20] vhost: correctly check the return value of translate_desc() in log_used()

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@xxxxxxxxxx>

[ Upstream commit 816db7663565cd23f74ed3d5c9240522e3fb0dda ]

When fail, translate_desc() returns negative value, otherwise the
number of iovs. So we should fail when the return value is negative
instead of a blindly check against zero.

Detected by CoverityScan, CID# 1442593:  Control flow issues  (DEADCODE)

Fixes: cc5e71075947 ("vhost: log dirty page correctly")
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Reported-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/vhost/vhost.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1696,7 +1696,7 @@ static int log_used(struct vhost_virtque
 
 	ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
 			     len, iov, 64, VHOST_ACCESS_WO);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	for (i = 0; i < ret; i++) {