linux-kernel - Re: [tip:perf/core] x86, mm, perf: Allow recursive faults from interrupts

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Date:	Fri, 17 Jan 2014 11:17:38 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Waiman Long <waiman.long@...com>
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Scott J Norton <scott.norton@...com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	tip-bot for Peter Zijlstra <tipbot@...or.com>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] x86, mm, perf: Allow recursive faults from interrupts

On Fri, Jan 17, 2014 at 10:10 AM, Waiman Long <waiman.long@...com> wrote:
> On 01/16/2014 08:39 AM, tip-bot for Peter Zijlstra wrote:
>>
>> Commit-ID:  c026b3591e4f2a4993df773183704bb31634e0bd
>> Gitweb:
>> http://git.kernel.org/tip/c026b3591e4f2a4993df773183704bb31634e0bd
>> Author:     Peter Zijlstra<peterz@...radead.org>
>> AuthorDate: Fri, 10 Jan 2014 21:06:03 +0100
>> Committer:  Ingo Molnar<mingo@...nel.org>
>> CommitDate: Thu, 16 Jan 2014 09:19:48 +0100
>>
>> x86, mm, perf: Allow recursive faults from interrupts
>>
>> Waiman managed to trigger a PMI while in a emulate_vsyscall() fault,
>> the PMI in turn managed to trigger a fault while obtaining a stack
>> trace. This triggered the sig_on_uaccess_error recursive fault logic
>> and killed the process dead.
>>
>> Fix this by explicitly excluding interrupts from the recursive fault
>> logic.
>>
>> Reported-and-Tested-by: Waiman Long<waiman.long@...com>
>> Fixes: e00b12e64be9 ("perf/x86: Further optimize copy_from_user_nmi()")
>> Cc: Aswin Chandramouleeswaran<aswin@...com>
>> Cc: Scott J Norton<scott.norton@...com>
>> Cc: Linus Torvalds<torvalds@...ux-foundation.org>
>> Cc: Andy Lutomirski<luto@...capital.net>
>> Cc: Arnaldo Carvalho de Melo<acme@...stprotocols.net>
>> Cc: Andrew Morton<akpm@...ux-foundation.org>
>> Signed-off-by: Peter Zijlstra<peterz@...radead.org>
>> Link:
>> http://lkml.kernel.org/r/20140110200603.GJ7572@laptop.programming.kicks-ass.net
>> Signed-off-by: Ingo Molnar<mingo@...nel.org>
>> ---
>>   arch/x86/mm/fault.c | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>
>>
>
> Will that be picked up by Linus as it is a 3.13 regression?

Does anyone actually know why this regressed recently?  The buggy code
has been there for quite a while.

--Andy
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