Re: [BUG] vhost/vringh: __get_user without access_ok leaks kernel memory via vDPA passthrough

[David Laight <david.laight.linux@gmail.com>]

On Sun, 18 Oct 2026 15:24:41 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Thu, Oct 15, 2026 at 03:23:45PM +0800, Haoran Wang wrote:
> > I'd like to report an issue in drivers/vhost/vringh.c:1216 (function
> > getu16_iotlb), found via static analysis of Linux 7.0.11 and verified
> > against the 7.2.10 source tree. I have reproduced the leak on an
> > unmodified 7.2.10 kernel.  
> 
> 
> This should fix it I think? Can you confirm pls?
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  drivers/vhost/vringh.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> index 9066f9f12ba1..4b097170bd36 100644
> --- a/drivers/vhost/vringh.c
> +++ b/drivers/vhost/vringh.c
> @@ -1213,7 +1213,11 @@ static inline int getu16_iotlb(const struct vringh *vrh,
>  		return ret;
>  
>  	if (vrh->use_va) {
> -		ret = __get_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
> +		__virtio16 __user *uaddr = ivec.iov.iovec[0].iov_base;
> +
> +		if (!access_ok(uaddr, sizeof(*p)))
> +			return -EFAULT;
> +		ret = __get_user(tmp, uaddr);

Can't that be a normal get_user() call?

David

>  		if (ret)
>  			return ret;
>  	} else {
> @@ -1251,7 +1255,11 @@ static inline int putu16_iotlb(const struct vringh *vrh,
>  	tmp = cpu_to_vringh16(vrh, val);
>  
>  	if (vrh->use_va) {
> -		ret = __put_user(tmp, (__virtio16 __user *)ivec.iov.iovec[0].iov_base);
> +		__virtio16 __user *uaddr = ivec.iov.iovec[0].iov_base;
> +
> +		if (!access_ok(uaddr, sizeof(*p)))
> +			return -EFAULT;
> +		ret = __put_user(tmp, uaddr);
>  		if (ret)
>  			return ret;
>  	} else {
> 
>