On Mon, Oct 11, 2010 at 07:22:57PM +0200, Dan Carpenter wrote:
> I did an audit for potential integer overflows of values which get passed
> to access_ok() and here are the results.
>
> Signed-off-by: Dan Carpenter <error27@xxxxxxxxx>
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index dd3d6f7..c2aa12c 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -429,6 +429,14 @@ static int vq_access_ok(unsigned int num,
> struct vring_avail __user *avail,
> struct vring_used __user *used)
> {
> +
> + if (num > UINT_MAX / sizeof *desc)
> + return 0;
> + if (num > UINT_MAX / sizeof *avail->ring - sizeof *avail)
> + return 0;
> + if (num > UINT_MAX / sizeof *used->ring - sizeof *used)
> + return 0;
> +
> return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
> access_ok(VERIFY_READ, avail,
> sizeof *avail + num * sizeof *avail->ring) &&
> @@ -447,6 +455,9 @@ int vhost_log_access_ok(struct vhost_dev *dev)
> /* Caller should have vq mutex and device mutex */
> static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
> {
> + if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used)
> + return 0;
> +
> return vq_memory_access_ok(log_base, vq->dev->memory,
> vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
> (!vq->log_used || log_access_ok(log_base, vq->log_addr,
> @@ -606,12 +617,17 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
> }
>
> /* Also validate log access for used ring if enabled. */
> - if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
> - !log_access_ok(vq->log_base, a.log_guest_addr,
> + if (a.flags & (0x1 << VHOST_VRING_F_LOG)) {
> + if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used) {
> + r = -EINVAL;
> + break;
> + }
> + if (!log_access_ok(vq->log_base, a.log_guest_addr,
> sizeof *vq->used +
> vq->num * sizeof *vq->used->ring)) {
> - r = -EINVAL;
> - break;
> + r = -EINVAL;
> + break;
> + }
> }
> }
>
As far as I can see, maximum value for num is 64K - 1:
if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
r = -EINVAL;
break;
}
How can any of the above two trigger?
It seems easier to check value for sanity at a single place where it's
passed from userspace to kernel.
--
MST
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