linux-kernel - Re: [PATCH 08/10] x86, pkeys: default to a restrictive init PKRU

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Message-ID: <CALCETrVW0taeuBjha1DEdafM5zZgbAHo=x1AJm=BafTEr++8Vg@mail.gmail.com>
Date:	Fri, 29 Jul 2016 12:44:24 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Linux API <linux-api@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrew Lutomirski <luto@...nel.org>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 08/10] x86, pkeys: default to a restrictive init PKRU

On Fri, Jul 29, 2016 at 10:50 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> On 07/29/2016 10:29 AM, Andy Lutomirski wrote:
>>> > In the end, this ensures that threads which do not know how to
>>> > manage their own pkey rights can not do damage to data which is
>>> > pkey-protected.
>> I think you missed the fpu__clear() caller in kernel/fpu/signal.c.
>>
>> ISTM it might be more comprehensible to change fpu__clear in general
>> and then special case things you want to behave differently.
>
> The code actually already patched the generic fpu__clear():
>
>         fpu__clear() ->
>         copy_init_fpstate_to_fpregs() ->
>         copy_init_pkru_to_fpregs()
>
> So I think it hit the case you are talking about.

Whoops, missed that.

-- 
Andy Lutomirski
AMA Capital Management, LLC