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Message-ID: <CAGXu5jJgYqkEkmfRdtgbtns=EyHc2UvzhkLFGgsYTTB3EKXJDQ@mail.gmail.com>
Date: Tue, 12 Jan 2016 15:54:32 -0800
From: Kees Cook <keescook@...omium.org>
To: Laura Abbott <labbott@...oraproject.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Mark Rutland <mark.rutland@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] arm64: Allow vmalloc regions to be set with set_memory_*
On Tue, Jan 12, 2016 at 3:22 PM, Laura Abbott <labbott@...oraproject.org> wrote:
>
> The range of set_memory_* is currently restricted to the module address
> range because of difficulties in breaking down larger block sizes.
> vmalloc maps PAGE_SIZE pages so it is safe to use as well. Update the
> function ranges and add a comment explaining why the range is restricted
> the way it is.
>
> Signed-off-by: Laura Abbott <labbott@...oraproject.org>
Acked-by: Kees Cook <keescook@...omium.org>
-Kees
> ---
> v2: Old version was sent out with vmalloc warnings. Sorry for the noise.
> ---
> arch/arm64/mm/pageattr.c | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 3571c73..88c8e54 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -36,6 +36,26 @@ static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
> return 0;
> }
>
> +static bool validate_addr(unsigned long start, unsigned long end)
> +{
> + /*
> + * This check explicitly excludes most kernel memory. Most kernel
> + * memory is mapped with a larger page size and breaking down the
> + * larger page size without causing TLB conflicts is very difficult.
> + *
> + * If you need to call set_memory_* on a range, the recommendation is
> + * to use vmalloc since that range is mapped with pages.
> + */
> + if (start >= MODULES_VADDR && start < MODULES_END &&
> + end >= MODULES_VADDR && end < MODULES_END)
> + return true;
> +
> + if (is_vmalloc_addr((void *)start) && is_vmalloc_addr((void *)end))
> + return true;
> +
> + return false;
> +}
> +
> static int change_memory_common(unsigned long addr, int numpages,
> pgprot_t set_mask, pgprot_t clear_mask)
> {
> @@ -51,10 +71,7 @@ static int change_memory_common(unsigned long addr, int numpages,
> WARN_ON_ONCE(1);
> }
>
> - if (start < MODULES_VADDR || start >= MODULES_END)
> - return -EINVAL;
> -
> - if (end < MODULES_VADDR || end >= MODULES_END)
> + if (!validate_addr(start, end))
> return -EINVAL;
>
> data.set_mask = set_mask;
> --
> 2.5.0
>
--
Kees Cook
Chrome OS & Brillo Security
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