vhost: validate log when IOTLB is enabled

BugLink: http://bugs.launchpad.net/bugs/1763366
[ Upstream commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ]

Vq log_base is the userspace address of bitmap which has nothing to do
with IOTLB. So it needs to be validated unconditionally otherwise we
may try use 0 as log_base which may lead to pin pages that will lead
unexpected result (e.g trigger BUG_ON() in set_bit_to_user()).

Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
Reported-by: syzbot+6304bf97ef436580fede@syzkaller.appspotmail.com
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f42683578dcabd832b0e6204e2ec0b4497c5705f..a5622a8364cbef97887069190857f2abc3bb33d8 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1256,14 +1256,12 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
 /* Caller should have vq mutex and device mutex */
 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 {
-       if (vq->iotlb) {
-               /* When device IOTLB was used, the access validation
-                * will be validated during prefetching.
-                */
-               return 1;
-       }
-       return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used) &&
-               vq_log_access_ok(vq, vq->log_base);
+       int ret = vq_log_access_ok(vq, vq->log_base);
+
+       if (ret || vq->iotlb)
+               return ret;
+
+       return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);