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Date: Tue, 14 Feb 2017 15:57:27 +0000
From: Mark Rutland <mark.rutland@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC: <linux-arm-kernel@...ts.infradead.org>, <catalin.marinas@....com>,
<will.deacon@....com>, <labbott@...oraproject.org>,
<kvmarm@...ts.cs.columbia.edu>, <marc.zyngier@....com>,
<andre.przywara@....com>, <Suzuki.Poulose@....com>, <james.morse@....com>,
<keescook@...omium.org>, <kernel-hardening@...ts.openwall.com>, <nd@....com>
Subject: Re: [PATCH v2 5/5] arm64: mmu: apply strict permissions to
.init.text and .init.data
On Sat, Feb 11, 2017 at 08:23:06PM +0000, Ard Biesheuvel wrote:
> To avoid having mappings that are writable and executable at the same
> time, split the init region into a .init.text region that is mapped
> read-only, and a .init.data region that is mapped non-executable.
>
> This is possible now that the alternative patching occurs via the linear
> mapping, and the linear alias of the init region is always mapped writable
> (but never executable).
>
> Since the alternatives descriptions themselves are read-only data, move
> those into the .init.text region.
>
> Reviewed-by: Laura Abbott <labbott@...hat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
This generally looks good.
As with my comment on patch 4, we might want to allow .init.text to be
mapped writeable for the sake of external debuggers.
Thanks,
Mark.
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index e97f1ce967ec..c53c43b4ed3f 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -479,12 +479,16 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end,
> */
> static void __init map_kernel(pgd_t *pgd)
> {
> - static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_init, vmlinux_data;
> + static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_inittext,
> + vmlinux_initdata, vmlinux_data;
>
> map_kernel_segment(pgd, _text, _etext, PAGE_KERNEL_ROX, &vmlinux_text);
> - map_kernel_segment(pgd, __start_rodata, __init_begin, PAGE_KERNEL, &vmlinux_rodata);
> - map_kernel_segment(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC,
> - &vmlinux_init);
> + map_kernel_segment(pgd, __start_rodata, __inittext_begin, PAGE_KERNEL,
> + &vmlinux_rodata);
> + map_kernel_segment(pgd, __inittext_begin, __inittext_end, PAGE_KERNEL_ROX,
> + &vmlinux_inittext);
> + map_kernel_segment(pgd, __initdata_begin, __initdata_end, PAGE_KERNEL,
> + &vmlinux_initdata);
> map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data);
>
> if (!pgd_val(*pgd_offset_raw(pgd, FIXADDR_START))) {
> --
> 2.7.4
>
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