linux-kernel - Re: [PATCH 3.19 3/3] x86, mpx: Change the MPX enable/disable API to arch

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Message-ID: <CALCETrWcG8SBoY6Zcb_2O-9hV5tbevjDYZ_SpfzB=km+tLW94g@mail.gmail.com>
Date:	Wed, 7 Jan 2015 15:24:52 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3.19 3/3] x86, mpx: Change the MPX enable/disable API to arch_prctl

On Wed, Jan 7, 2015 at 3:18 PM, Dave Hansen <dave.hansen@...ux.intel.com> wrote:
> On 01/05/2015 03:04 PM, Andy Lutomirski wrote:
>> Anyway, if it's actually a problem to change it, I have no real
>> problem keeping it, but I think we *really* need to validate the rest
>> of the arguments at the very least.
>
> If we "validate" the arguments like you suggested, then a call like this:
>
>         prctl(PR_MPX_DISABLE_MANAGEMENT);
>
> ends up returning -EINVAL:
>
>> prctl(0x2b /* PR_??? */, 0x7fffffd3, 0x7f360955e9e0, 0x2c, 0x7f3609314840) = -1 EINVAL (Invalid argument)
>
> A quick grep through ltp and some other source I have laying around does
> *not* show folks adding 0's to these calls for "empty" arguments.  Is
> this really something we want to do?
>
>         prctl(PR_MPX_DISABLE_MANAGEMENT, 0, 0, 0, 0);

Yes, because we might want to do prctl(PR_MPX_ENABLE_MANAGEMENT, x, y,
z, 0) some day.

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC
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