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From: Thomas Gleixner <tglx@linutronix.de>
To: "Yu\, Yu-cheng" <yu-cheng.yu@intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Cc: linux-tip-commits@vger.kernel.org,
	Fenghua Yu <fenghua.yu@intel.com>, Borislav Petkov <bp@suse.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Tony Luck <tony.luck@intel.com>, x86 <x86@kernel.org>, "Shankar\,
	Ravi V" <ravi.v.shankar@intel.com>
Subject: Re: [tip: x86/fpu] x86/fpu/xstate: Define new functions for clearing fpregs and xstates
Date: Tue, 25 May 2021 20:00:12 +0200	[thread overview]
Message-ID: <87y2c28zir.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <10a553a5-699f-6921-705e-9afa1a8e42de@intel.com>

On Tue, May 25 2021 at 10:44, Yu-cheng Yu wrote:
> On 5/24/2021 9:34 AM, Andy Lutomirski wrote:
>> So I'm guessing that syzbot may have misattributed the problem.  But
>> we definitely need to clean up the XRSTOR #GP handling before CET
>> lands.
>> 
>  From the crash dump, the system is doing syscall_exit_to_user_mode() 
> for __x64_sys_futex().  The futex syscall does not seem to modify 
> xstates,

Of course does the futex syscall not modify anything, but the task can
schedule out before returning from the syscall so it has to restore the
FPU state.

> but upon returning to user mode, XRSTORS gets a GP.  Can this 
> be some memory corruption?  fpu__clear() is merely helping to clear the 
> mess and seems to be innocent.

What kind of analysis is that?

Thanks,

        tglx

  reply	other threads:[~2021-05-25 18:00 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-12 14:54 [PATCH v4 00/10] Support XSAVES supervisor states Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 01/10] x86/fpu/xstate: Rename validate_xstate_header() to validate_user_xstate_header() Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Fenghua Yu
2020-05-12 14:54 ` [PATCH v4 02/10] x86/fpu/xstate: Define new macros for supervisor and user xstates Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Fenghua Yu
2020-05-12 14:54 ` [PATCH v4 03/10] x86/fpu/xstate: Separate user and supervisor xfeatures mask Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 04/10] x86/fpu/xstate: Introduce XSAVES supervisor states Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 05/10] x86/fpu/xstate: Define new functions for clearing fpregs and xstates Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Fenghua Yu
2021-05-24 16:34     ` Andy Lutomirski
2021-05-25 17:44       ` Yu, Yu-cheng
2021-05-25 18:00         ` Thomas Gleixner [this message]
2022-11-29 11:19           ` Ivan Zahariev
2022-11-29 18:16             ` Dave Hansen
2022-12-01 12:58               ` Ivan Zahariev
2022-12-01 14:04                 ` Dave Hansen
2020-05-12 14:54 ` [PATCH v4 06/10] x86/fpu/xstate: Update sanitize_restored_xstate() for supervisor xstates Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 07/10] x86/fpu/xstate: Update copy_kernel_to_xregs_err() for XSAVES supervisor states Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] x86/fpu/xstate: Update copy_kernel_to_xregs_err() for " tip-bot2 for Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 08/10] x86/fpu: Introduce copy_supervisor_to_kernel() Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 09/10] x86/fpu/xstate: Preserve supervisor states for slow path of __fpu__restore_sig() Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] x86/fpu/xstate: Preserve supervisor states for the slow path in __fpu__restore_sig() tip-bot2 for Yu-cheng Yu
2020-05-12 14:54 ` [PATCH v4 10/10] x86/fpu/xstate: Restore supervisor states for signal return Yu-cheng Yu
2020-05-16 15:10   ` [tip: x86/fpu] " tip-bot2 for Yu-cheng Yu

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