| Message ID | 1522310404-8486-1-git-send-email-jasowang@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@syzkaller.appspotmail.com > Signed-off-by: Jason Wang <jasowang@redhat.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> stable material I guess. > --- > 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
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@syzkaller.appspotmail.com > Signed-off-by: Jason Wang <jasowang@redhat.com> 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
From: "Michael S. Tsirkin" <mst@redhat.com> Date: Thu, 29 Mar 2018 15:48:22 +0300 > 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@syzkaller.appspotmail.com >> Signed-off-by: Jason Wang <jasowang@redhat.com> > > Acked-by: Michael S. Tsirkin <mst@redhat.com> > > stable material I guess. Applied and queued up for -stable.
On 2018年03月29日 22:44, Michael S. Tsirkin wrote: > 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@syzkaller.appspotmail.com >> Signed-off-by: Jason Wang<jasowang@redhat.com> > 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? > > Looking at get_user_pages_fast(), it has: if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, (void __user *)start, len))) return 0; So this is expected I think. Thanks
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);
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> --- drivers/vhost/vhost.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)