Re: [PATCH v19 02/15] arm64: Introduce prctl() options to control the tagged user addresses ABI

[Catalin Marinas]

On Tue, Jul 23, 2019 at 07:58:39PM +0200, Andrey Konovalov wrote:
> From: Catalin Marinas <catalin.marinas@xxxxxxx>
> 
> It is not desirable to relax the ABI to allow tagged user addresses into
> the kernel indiscriminately. This patch introduces a prctl() interface
> for enabling or disabling the tagged ABI with a global sysctl control
> for preventing applications from enabling the relaxed ABI (meant for
> testing user-space prctl() return error checking without reconfiguring
> the kernel). The ABI properties are inherited by threads of the same
> application and fork()'ed children but cleared on execve(). A Kconfig
> option allows the overall disabling of the relaxed ABI.
> 
> The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle
> MTE-specific settings like imprecise vs precise exceptions.
> 
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Following several discussions on the list and in private, I'm proposing
the update below. I can send it as a patch on top of the current series
since Will has already queued this.

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