From: Borislav Petkov <bp@alien8.de>
To: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
nslusarek@gmx.net, Linus Torvalds <torvalds@linux-foundation.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf: Fix sys_perf_event_open() race against self
Date: Wed, 16 Nov 2022 23:30:50 +0100 [thread overview]
Message-ID: <Y3Vkmvi2vib7fwHn@zn.tnic> (raw)
In-Reply-To: <700710fc-1ac1-1b39-0e63-eb86adb4b984@amd.com>
On Mon, May 23, 2022 at 04:03:29PM +0530, Ravi Bangoria wrote:
> On 21-May-22 12:08 AM, Peter Zijlstra wrote:
> >
> > Norbert reported that it's possible to race sys_perf_event_open() such
> > that the looser ends up in another context from the group leader,
> > triggering many WARNs.
> >
> > The move_group case checks for races against itself, but the
> > !move_group case doesn't, seemingly relying on the previous
> > group_leader->ctx == ctx check. However, that check is racy due to not
> > holding any locks at that time.
> >
> > Therefore, re-check the result after acquiring locks and bailing
> > if they no longer match.
> >
> > Additionally, clarify the not_move_group case from the
> > move_group-vs-move_group race.
>
> Tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
>
> Below is a quick test to reproduce the issue. It triggers WARN_ON()
> as normal user. No warnings with the patch.
Shouldn't this test be in tools/perf/tests/ or so?
If that hasn't happened yet, I mean.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2022-11-16 22:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-20 18:38 [PATCH] perf: Fix sys_perf_event_open() race against self Peter Zijlstra
2022-05-23 10:33 ` Ravi Bangoria
2022-11-16 22:30 ` Borislav Petkov [this message]
2022-11-17 10:33 ` Ravi Bangoria
2022-11-17 10:40 ` Borislav Petkov
2022-11-17 10:59 ` Ravi Bangoria
2022-11-17 11:59 ` Borislav Petkov
2022-11-17 13:38 ` Ravi Bangoria
2022-05-23 10:48 ` Mark Rutland
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