vhost: correctly check the return value of translate_desc() in log_used()

BugLink: https://bugs.launchpad.net/bugs/1837813
[ 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@redhat.com>
Reported-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index d83ead14b16a1c87993d7ba572e179ac63a17481..7cbc18bdaf672f4b5b9c48c9f8f04fe0220eaf8a 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1780,7 +1780,7 @@ static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
 
        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++) {