On Thu, Mar 29, 2018 at 04:00:04PM +0800, Jason Wang wrote: > 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@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx> One follow-up question: We still observe that get user pages returns 0 sometimes. While I agree we should not pass in unvalidated addresses, isn't this worth documenting? > --- > drivers/vhost/vhost.c | 14 ++++++-------- > 1 file changed, 6 insertions(+), 8 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 5d5a9d9..5320039 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1244,14 +1244,12 @@ 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); > > -- > 2.7.4 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization