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    SubjectRe: [PATCH 4.14 134/138] vhost: validate log when IOTLB is enabled
    On Wed, Apr 11, 2018 at 12:25:24AM +0200, Greg Kroah-Hartman wrote:
    > 4.14-stable review patch. If anyone has any objections, please let me know.
    >
    > ------------------
    >
    > From: Jason Wang <jasowang@redhat.com>
    >
    >
    > [ 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>
    > ---
    > drivers/vhost/vhost.c | 14 ++++++--------
    > 1 file changed, 6 insertions(+), 8 deletions(-)
    >
    > --- a/drivers/vhost/vhost.c
    > +++ b/drivers/vhost/vhost.c
    > @@ -1252,14 +1252,12 @@ static int vq_log_access_ok(struct vhost
    > /* 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)

    That's a bug, davem just queued a patch to fix this upstream.

    > + return ret;
    > +
    > + return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
    > }
    > EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
    >
    >

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