linux-kernel - Re: [PATCH] mm: Prevent mapping typed pages to userspace

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Message-ID: <CAGXu5jLbC1-T9JbYcDcXjA2G3jv3DLCWSUvJf3KiA8so2XC19g@mail.gmail.com>
Date:   Tue, 29 Jan 2019 21:09:30 +1300
From:   Kees Cook <keescook@...omium.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] mm: Prevent mapping typed pages to userspace

On Tue, Jan 29, 2019 at 6:38 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> Pages which use page_type must never be mapped to userspace as it would
> destroy their page type.  Add an explicit check for this instead of
> assuming that kernel drivers always get this right.
>
> Signed-off-by: Matthew Wilcox <willy@...radead.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  mm/memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index ce8c90b752be..db3534bbd652 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) || PageSlab(page))
> +       if (PageAnon(page) || PageSlab(page) || page_has_type(page))
>                 goto out;
>         retval = -ENOMEM;
>         flush_dcache_page(page);
> --
> 2.20.1
>


-- 
Kees Cook