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Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only

From Ard Biesheuvel <ard.biesheuvel@linaro.org>
Newsgroups linux.kernel
Subject Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only
Date 2016-02-13 10:10 +0100
Message-ID <r1Enf-2IH-1@gated-at.bofh.it> (permalink)
References <r0KXM-7U9-13@gated-at.bofh.it> <r10gd-1uu-79@gated-at.bofh.it> <r1wpH-5UM-3@gated-at.bofh.it>
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On 13 February 2016 at 01:31, David Brown <david.brown@linaro.org> wrote:
> On Thu, Feb 11, 2016 at 03:19:20PM +0100, Ard Biesheuvel wrote:
>
>>> diff --git a/arch/arm64/kernel/vdso/vdso.S
>>> b/arch/arm64/kernel/vdso/vdso.S
>>> index 60c1db5..db7c0f2 100644
>>> --- a/arch/arm64/kernel/vdso/vdso.S
>>> +++ b/arch/arm64/kernel/vdso/vdso.S
>>> @@ -24,6 +24,7 @@
>>>         __PAGE_ALIGNED_DATA
>>
>>
>> ^^ You can get rid of this now as well
>
>
> Can we?  The page is getting mapped to userspace, and if we didn't
> page align it, we could leak kernel read-only data to every userspace
> process.
>

That's what the .balign is for. __PAGE_ALIGNED_DATA only sets the
section, and you're overriding that right after.

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Thread

[PATCH] arm64: vdso: Mark vDSO code as read-only David Brown <david.brown@linaro.org> - 2016-02-10 23:00 +0100
  Re: [PATCH] arm64: vdso: Mark vDSO code as read-only Will Deacon <will.deacon@arm.com> - 2016-02-11 14:50 +0100
  Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-11 15:20 +0100
    Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as  read-only David Brown <david.brown@linaro.org> - 2016-02-13 01:40 +0100
      Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-13 10:10 +0100
  Re: [PATCH] arm64: vdso: Mark vDSO code as read-only Catalin Marinas <catalin.marinas@arm.com> - 2016-02-16 19:30 +0100

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