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

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Date:	Fri, 29 Jul 2016 10:50:51 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Andy Lutomirski <luto@...capital.net>
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 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.