From: Michael S. Tsirkin <mst@redhat.com>
Date: Tue, 14 Sep 2010 13:15:52 +0000 (+0200)
Subject: vhost-net: fix range checking in mrg bufs case
X-Git-Tag: upstream/snapshot3+hdmi~12792^2~41^2~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ee05d6939ed17b55e9c2466af32c208e0d547eb8;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

vhost-net: fix range checking in mrg bufs case

In mergeable buffer case, we use headcount, log_num
and seg as indexes in same-size arrays, and
we know that headcount <= seg and
log_num equals either 0 or seg.

Therefore, the right thing to do is range-check seg,
not headcount as we do now: these will be different
if guest chains s/g descriptors (this does not
happen now, but we can not trust the guest).

Long term, we should add BUG_ON checks to verify
two other indexes are what we think they should be.

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 29e850a..7c80082 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -243,7 +243,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 	int r, nlogs = 0;
 
 	while (datalen > 0) {
-		if (unlikely(headcount >= VHOST_NET_MAX_SG)) {
+		if (unlikely(seg >= VHOST_NET_MAX_SG)) {
 			r = -ENOBUFS;
 			goto err;
 		}