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

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Message-ID: <20160213003147.GA12074@davidb.org>
Date:	Fri, 12 Feb 2016 17:31:47 -0700
From:	David Brown <david.brown@...aro.org>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	kernel-hardening@...ts.openwall.com,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as
 read-only

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.

David