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Date: Tue, 16 Feb 2016 22:20:10 -0700
From: David Brown <>
To: Kees Cook <>
Cc: Russell King <>,
	"" <>,
	"" <>,
	Ingo Molnar <>,
	Andy Lutomirski <>,
	"H. Peter Anvin" <>,
	Michael Ellerman <>,
	Mathias Krause <>,
	Thomas Gleixner <>,
	"" <>, Arnd Bergmann <>,
	PaX Team <>, Emese Revfy <>,
	LKML <>,
	linux-arch <>
Subject: Re: [PATCH] ARM: vdso: Mark vDSO code as read-only

On Tue, Feb 16, 2016 at 01:52:33PM -0800, Kees Cook wrote:
>On Tue, Feb 16, 2016 at 1:36 PM, David Brown <> wrote:
>> Although the arm vDSO is cleanly separated by code/data with the code
>> being read-only in userspace mappings, the code page is still writable
>> from the kernel.  There have been exploits (such as
>> that take advantage of this on x86 to go
>> from a bad kernel write to full root.
>> Prevent this specific exploit on arm by putting the vDSO code page in
>> post-init read-only memory as well.
>Is the vdso dynamically built at init time like on x86, or can this
>just use .rodata directly?

On ARM, it is patched during init.  Arm64's is just plain read-only.


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