Re: perf: use-after-free in perf_release

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: perf: use-after-free in perf_release
Date	2017-03-07 18:40 +0100
Message-ID	<tirfA-2oi-13@gated-at.bofh.it> (permalink)
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On Tue, Mar 07, 2017 at 05:51:32PM +0100, Oleg Nesterov wrote:
> On 03/07, Dmitry Vyukov wrote:

> > I would what is that that is failed in copy_process. Could it be
> > perf_event_init_task itself? Maybe it leaves a pointer to p in some
> > shared state on some error conditions?
> 
> I am looking at perf_event_init_task() too and I can't understand the
> error handling...
> 
> perf_event_init_context() can return success even if inherit_task_group() in
> the first list_for_each_entry(pinned_groups) fails, "ret" will be overwritten
> by the 2nd list_for_each_entry(flexible_groups) loop. "inherited_all" should
> be cleared, still this looks confusing at least.
> 
> inherit_event() returns NULL under is_orphaned_event() check, not ERR_PTR().
> Is it correct?

Urgh, there was something tricky there, but I cannot remember, and it
seems we didn't put a comment in either :/

Alexander, can you remember?

But yes, this all looks a tad dodgy, I'll try and have a look, but I
feel like I'm coming down with something :-(

Thread

perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-06 11:00 +0100
  Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-06 13:20 +0100
    Re: perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-06 13:20 +0100
      Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-06 13:30 +0100
        Re: perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-06 13:40 +0100
          Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-06 13:50 +0100
  Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-06 14:30 +0100
    Re: perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-06 14:40 +0100
      Re: perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 10:30 +0100
        Re: perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 10:50 +0100
          Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-07 12:50 +0100
        Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-07 11:40 +0100
      Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-07 10:50 +0100
    Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-07 14:20 +0100
      Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-07 15:10 +0100
    Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-07 15:10 +0100
      Re: perf: use-after-free in perf_release Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 15:30 +0100
        Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-07 18:40 +0100
        Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-07 18:50 +0100

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