[PATCH v8 32/50] vhost: switch to __get/__put_user exclusively

Michael S. Tsirkin
2014-12-01T16:05:25Z

Most places in vhost can use __get/__put_user rather than
get/put_user since addresses are pre-validated.
This should be good for performance, but this also
will help make code sparse-clean: get/put_user macros
don't play well with __virtioXX bitwise tags.
Switch to get/put_user to __ variants everywhere in vhost.
There's one exception - for consistency switch that
as well, and add an explicit access_ok check.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
drivers/vhost/vhost.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c90f437..6a40837 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1038,6 +1038,7 @@ static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)

int vhost_init_used(struct vhost_virtqueue *vq)
{
+ u16 last_used_idx;
int r;
if (!vq->private_data)
return 0;
@@ -1046,7 +1047,13 @@ int vhost_init_used(struct vhost_virtqueue *vq)
if (r)
return r;
vq->signalled_used_valid = false;
- return get_user(vq->last_used_idx, &vq->used->idx);
+ if (!access_ok(VERIFY_READ, &vq->used->idx, sizeof vq->used->idx))
+ return -EFAULT;
+ r = __get_user(last_used_idx, &vq->used->idx);
+ if (r)
+ return r;
+ vq->last_used_idx = last_used_idx;
+ return 0;
}
EXPORT_SYMBOL_GPL(vhost_init_used);

@@ -1404,7 +1411,7 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,

/* Make sure buffer is written before we update index. */
smp_wmb();
- if (put_user(vq->last_used_idx, &vq->used->idx)) {
+ if (__put_user(vq->last_used_idx, &vq->used->idx)) {
vq_err(vq, "Failed to increment used idx");
return -EFAULT;
}
@@ -1449,7 +1456,7 @@ static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
if (unlikely(!v))
return true;

- if (get_user(event, vhost_used_event(vq))) {
+ if (__get_user(event, vhost_used_event(vq))) {
vq_err(vq, "Failed to get used event idx");
return true;
}
--
MST