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From: Eric Dumazet <edumazet@google.com>
To: syzkaller <syzkaller@googlegroups.com>,
	Eric Dumazet <edumazet@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	acme@redhat.com, Linus Torvalds <torvalds@linux-foundation.org>,
	Alexander Potapenko <glider@google.com>,
	Kostya Serebryany <kcc@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Sasha Levin <sasha.levin@oracle.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	jolsa@redhat.com, Ingo Molnar <mingo@kernel.org>,
	vincent.weaver@maine.edu, Thomas Gleixner <tglx@linutronix.de>,
	acme@kernel.org, Stephane Eranian <eranian@google.com>
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] perf: Fix race in perf_event_exec()
Date: Wed, 6 Jan 2016 13:56:56 -0500	[thread overview]
Message-ID: <CANn89iLzUuR6wM=hOybM25d21PN=Fax5Ms7z2XeArTwAhZ6zqQ@mail.gmail.com> (raw)
In-Reply-To: <tip-c127449944659543e5e2423002f08f0af98dba5c@git.kernel.org>

On Wed, Jan 6, 2016 at 1:46 PM, tip-bot for Peter Zijlstra
<tipbot@zytor.com> wrote:

>
> This is because context switches can swap the task_struct::perf_event_ctxp[]
> pointer around. Therefore you have to either disable preemption when looking
> at current, or hold ctx->lock.
>


>
>  void perf_event_exec(void)
>  {
> -       struct perf_event_context *ctx;
>         int ctxn;
>
>         rcu_read_lock();

Do we still need this rcu_read_lock(), if perf_event_enable_on_exec()
uses  local_irq_save( ?

> -       for_each_task_context_nr(ctxn) {
> -               ctx = current->perf_event_ctxp[ctxn];
> -               if (!ctx)
> -                       continue;
> -
> -               perf_event_enable_on_exec(ctx);
> -       }
> +       for_each_task_context_nr(ctxn)
> +               perf_event_enable_on_exec(ctxn);
>         rcu_read_unlock();
>  }
>

  reply	other threads:[~2016-01-06 18:57 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-04 20:04 use-after-free in __perf_install_in_context Dmitry Vyukov
2015-12-04 20:32 ` Alexei Starovoitov
2015-12-04 21:00   ` Dmitry Vyukov
2015-12-07 11:04     ` Dmitry Vyukov
2015-12-07 11:06       ` Dmitry Vyukov
2015-12-07 11:24         ` Dmitry Vyukov
2015-12-07 15:36 ` Peter Zijlstra
2015-12-07 16:09   ` Dmitry Vyukov
2015-12-08  3:24     ` Alexei Starovoitov
2015-12-08 16:12       ` Dmitry Vyukov
2015-12-08 17:54         ` Alexei Starovoitov
2015-12-08 17:56           ` Dmitry Vyukov
2015-12-08 18:05             ` Alexei Starovoitov
2015-12-08 18:35               ` Dmitry Vyukov
2015-12-08 19:56                 ` Alexei Starovoitov
2015-12-09  9:17                   ` Dmitry Vyukov
2015-12-10  3:54                     ` Alexei Starovoitov
2015-12-10  9:02                       ` Peter Zijlstra
2015-12-10 17:03                         ` Alexei Starovoitov
2015-12-11  8:14                           ` Ingo Molnar
2015-12-15 13:11                             ` Dmitry Vyukov
2015-12-08 16:44     ` Peter Zijlstra
2015-12-08 19:14       ` Dmitry Vyukov
2015-12-10 19:57         ` Peter Zijlstra
2015-12-15 13:09           ` Dmitry Vyukov
2015-12-17 14:06           ` Peter Zijlstra
2015-12-17 14:08             ` Dmitry Vyukov
2015-12-17 14:26               ` Peter Zijlstra
2015-12-17 14:28                 ` Peter Zijlstra
2015-12-17 14:35                   ` Dmitry Vyukov
2015-12-17 14:43                     ` Peter Zijlstra
2015-12-31 17:15                       ` Dmitry Vyukov
2016-01-05 12:17                         ` Peter Zijlstra
2016-01-08  8:40                           ` Dmitry Vyukov
2016-01-08 10:28                             ` Dmitry Vyukov
2016-01-06 18:46           ` [tip:perf/core] perf: Fix race in perf_event_exec() tip-bot for Peter Zijlstra
2016-01-06 18:56             ` Eric Dumazet [this message]
2016-01-07 13:40               ` Peter Zijlstra
2016-01-07 16:26                 ` Paul E. McKenney
2016-01-07 16:36                   ` Eric Dumazet
2016-01-07 16:46                     ` Paul E. McKenney
2015-12-08 16:22 ` use-after-free in __perf_install_in_context Peter Zijlstra
2015-12-08 18:57   ` Ingo Molnar
2015-12-09  9:05     ` Peter Zijlstra
2015-12-08 16:27 ` Peter Zijlstra
2015-12-08 16:50   ` Dmitry Vyukov

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