Re: [PATCH] mm: Prevent mapping slab pages to userspace

[Pekka Enberg]

On 25/01/2019 19.38, Matthew Wilcox wrote:
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
>
> Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>

Acked-by: Pekka Enberg <penberg@xxxxxxxxxx>

A WARN_ON_ONCE() would be nice here to let those buggy drivers know that 
they will no longer work.

> ---
>   mm/memory.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e11ca9dd823f..ce8c90b752be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1451,7 +1451,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
>   	spinlock_t *ptl;
>   
>   	retval = -EINVAL;
> -	if (PageAnon(page))
> +	if (PageAnon(page) || PageSlab(page))
>   		goto out;
>   	retval = -ENOMEM;
>   	flush_dcache_page(page);