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From: Borislav Petkov <bp@alien8.de>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: x86@kernel.org, Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Darren Hart <dvhart@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH v3] x86/mce: Avoid infinite loop for copy from user recovery
Date: Mon, 18 Jan 2021 16:39:39 +0100	[thread overview]
Message-ID: <20210118153939.GC30090@zn.tnic> (raw)
In-Reply-To: <20210115193435.GA4663@agluck-desk2.amr.corp.intel.com>

On Fri, Jan 15, 2021 at 11:34:35AM -0800, Luck, Tony wrote:
> In the user mode case we should only bump mce_count to "1" and
> before task_work() gets called.

Ok, right, it should not be possible to trigger a second MCE while
queue_task_work() runs when it is a user MCE. The handler itself won't
touch the page with the hw error so our assumption is that it'll get
poisoned.

If it doesn't, I guess the memory failure code will kill the process
yadda yadda...

> It shouldn't hurt to do the same checks. Maybe it will catch something
> weird - like an NMI handler on return from the machine check doing a
> get_user() that hits another machine check during the return from this
> machine check.

Eww.

> AndyL has made me extra paranoid. :-)

Yeah, he comes up with the nuttiest scenarios. :-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  parent reply	other threads:[~2021-01-18 15:47 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-08 22:22 [PATCH 0/2] Fix infinite machine check loop in futex_wait_setup() Tony Luck
2021-01-08 22:22 ` [PATCH 1/2] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-08 22:22 ` [PATCH 2/2] futex, x86/mce: Avoid double machine checks Tony Luck
2021-01-08 22:47   ` Peter Zijlstra
2021-01-08 23:08     ` Luck, Tony
2021-01-08 23:14       ` Peter Zijlstra
2021-01-08 23:20         ` Luck, Tony
2021-01-11 21:44 ` [PATCH v2 0/3] Fix infinite machine check loop in futex_wait_setup() Tony Luck
2021-01-11 21:44   ` [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-11 22:11     ` Andy Lutomirski
2021-01-11 22:20       ` Luck, Tony
2021-01-12 17:00         ` Andy Lutomirski
2021-01-12 17:16           ` Luck, Tony
2021-01-12 17:21             ` Andy Lutomirski
2021-01-12 18:23               ` Luck, Tony
2021-01-12 18:57                 ` Andy Lutomirski
2021-01-12 20:52                   ` Luck, Tony
2021-01-12 22:04                     ` Andy Lutomirski
2021-01-13  1:50                       ` Luck, Tony
2021-01-13  4:15                         ` Andy Lutomirski
2021-01-13 10:00                           ` Borislav Petkov
2021-01-13 16:06                             ` Luck, Tony
2021-01-13 16:19                               ` Borislav Petkov
2021-01-13 16:32                                 ` Luck, Tony
2021-01-13 17:35                                   ` Borislav Petkov
2021-01-14 20:22     ` Borislav Petkov
2021-01-14 21:05       ` Luck, Tony
2021-01-11 21:44   ` [PATCH v2 2/3] x86/mce: Add new return value to get_user() for machine check Tony Luck
2021-01-11 21:44   ` [PATCH v2 3/3] futex, x86/mce: Avoid double machine checks Tony Luck
2021-01-14 17:22   ` [PATCH v2 0/3] Fix infinite machine check loop in futex_wait_setup() Andy Lutomirski
2021-01-15  0:38   ` [PATCH v3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-15 15:27     ` Borislav Petkov
2021-01-15 19:34       ` Luck, Tony
2021-01-15 20:51         ` [PATCH v4] " Luck, Tony
2021-01-15 23:23           ` Luck, Tony
2021-01-19 10:56             ` Borislav Petkov
2021-01-19 23:57               ` Luck, Tony
2021-01-20 12:18                 ` Borislav Petkov
2021-01-20 17:17                   ` Luck, Tony
2021-01-21 21:09                   ` Luck, Tony
2021-01-25 22:55                     ` [PATCH v5] " Luck, Tony
2021-01-26 11:03                       ` Borislav Petkov
2021-01-26 22:36                         ` Luck, Tony
2021-01-28 17:57                           ` Borislav Petkov
2021-02-01 18:58                             ` Luck, Tony
2021-02-02 11:01                               ` Borislav Petkov
2021-02-02 16:04                                 ` Luck, Tony
2021-02-02 21:06                                   ` Borislav Petkov
2021-02-02 22:12                                     ` Luck, Tony
2021-01-18 15:39         ` Borislav Petkov [this message]
2021-07-06 19:06 [PATCH 0/3] More machine check recovery fixes Tony Luck
2021-08-18  0:29 ` [PATCH v2 " Tony Luck
2021-08-18  0:29   ` [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-09-13  9:24     ` Borislav Petkov
2021-09-13 21:52       ` [PATCH v3] " Luck, Tony
2021-09-14  8:28         ` Borislav Petkov

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