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

[Andy Lutomirski]

On Fri, Jan 17, 2014 at 10:10 AM, Waiman Long <waiman.long@xxxxxx> 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@xxxxxxxxxxxxx>
>> AuthorDate: Fri, 10 Jan 2014 21:06:03 +0100
>> Committer:  Ingo Molnar<mingo@xxxxxxxxxx>
>> 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@xxxxxx>
>> Fixes: e00b12e64be9 ("perf/x86: Further optimize copy_from_user_nmi()")
>> Cc: Aswin Chandramouleeswaran<aswin@xxxxxx>
>> Cc: Scott J Norton<scott.norton@xxxxxx>
>> Cc: Linus Torvalds<torvalds@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Andy Lutomirski<luto@xxxxxxxxxxxxxx>
>> Cc: Arnaldo Carvalho de Melo<acme@xxxxxxxxxxxxxxxxxx>
>> Cc: Andrew Morton<akpm@xxxxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Peter Zijlstra<peterz@xxxxxxxxxxxxx>
>> Link:
>> http://lkml.kernel.org/r/20140110200603.GJ7572@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> Signed-off-by: Ingo Molnar<mingo@xxxxxxxxxx>
>> ---
>>   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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