From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave.hansen@intel.com>, LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Tony Luck <tony.luck@intel.com>,
Yu-cheng Yu <yu-cheng.yu@intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage
Date: Tue, 08 Jun 2021 14:27:54 +0200 [thread overview]
Message-ID: <875yyozgl1.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <878s3kzjtx.ffs@nanos.tec.linutronix.de>
On Tue, Jun 08 2021 at 13:17, Thomas Gleixner wrote:
> On Mon, Jun 07 2021 at 09:38, Dave Hansen wrote:
>> On 6/7/21 7:08 AM, Thomas Gleixner wrote:
>>>> By the way, are you talking specifically about the _error_ paths where
>>>> the kernel is unable to XRSTOR the signal XSAVE buffer for some reason,
>>>> and tries to apply either init_fpu or the hardware init state instead?
>>>
>>> 1) Successful XRSTOR from user if the PKRU feature bit in the
>>> sigframe xsave.header.xfeatures is cleared. Both fast and slow path.
>>
>> It seems like the suggestion here is to inject 'init_pkru_value' in all
>> cases where the kernel would be injecting the hardware init value. I
>> don't think we should go that far.
>>
>> If a signal handler sets xsave.header.xfeatures[PKRU]=0, I can't imagine
>> any other intent than wanting the hardware init value.
>
> Fine. But PKRU=0 is broken today...
>
> T1 in user space
> wrpkru(0)
It's actually not wrpkru(0), but a XRSTOR with the
xsave.header.xfeatures[PKRU] bit cleared. But the rest is the same...
prev parent reply other threads:[~2021-06-08 12:27 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-05 23:47 [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage Thomas Gleixner
2021-06-05 23:47 ` [patch V2 01/14] selftests/x86: Test signal frame XSTATE header corruption handling Thomas Gleixner
2021-06-05 23:47 ` [patch V2 02/14] x86/fpu: Prevent state corruption in __fpu__restore_sig() Thomas Gleixner
2021-06-07 8:49 ` Borislav Petkov
2021-06-05 23:47 ` [patch V2 03/14] x86/fpu: Invalidate FPU state after a failed XRSTOR from a user buffer Thomas Gleixner
2021-06-05 23:47 ` [patch V2 04/14] x86/pkru: Make the fpinit state update work Thomas Gleixner
2021-06-07 15:18 ` Borislav Petkov
2021-06-05 23:47 ` [patch V2 05/14] x86/fpu: Limit xstate copy size in xstateregs_set() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 06/14] x86/fpu: Sanitize xstateregs_set() Thomas Gleixner
2021-06-07 19:39 ` Borislav Petkov
2021-06-05 23:47 ` [patch V2 07/14] x86/fpu: Add address range checks to copy_user_to_xstate() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 08/14] x86/fpu: Move inlines where they belong Thomas Gleixner
2021-06-05 23:47 ` [patch V2 09/14] x86/cpu: Sanitize X86_FEATURE_OSPKE Thomas Gleixner
2021-06-05 23:47 ` [patch V2 10/14] x86/fpu: Rename fpu__clear_all() to fpu_flush_thread() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 11/14] x86/pkru: Provide pkru_get_init_value() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 12/14] x86/fpu: Clean up the fpu__clear() variants Thomas Gleixner
2021-06-05 23:47 ` [patch V2 13/14] x86/fpu: Rename xstate copy functions which are related to UABI Thomas Gleixner
2021-06-05 23:47 ` [patch V2 14/14] x86/fpu: Deduplicate copy_uabi_from_user/kernel_to_xstate() Thomas Gleixner
2021-06-07 13:02 ` [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage Thomas Gleixner
2021-06-07 13:36 ` Dave Hansen
2021-06-07 14:08 ` Thomas Gleixner
2021-06-07 16:38 ` Dave Hansen
2021-06-07 22:51 ` Thomas Gleixner
2021-06-08 14:47 ` Dave Hansen
2021-06-08 11:17 ` Thomas Gleixner
2021-06-08 12:27 ` Thomas Gleixner [this message]
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