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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
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