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Groups > linux.kernel > #1600620

Re: perf: use-after-free in perf_release

From Oleg Nesterov <oleg@redhat.com>
Newsgroups linux.kernel
Subject Re: perf: use-after-free in perf_release
Date 2017-03-14 16:40 +0100
Message-ID <tkWIj-25L-23@gated-at.bofh.it> (permalink)
References (5 earlier) <tkVjb-1eJ-13@gated-at.bofh.it> <tkVjc-1eJ-41@gated-at.bofh.it> <tkVMd-1qV-13@gated-at.bofh.it> <tkWff-1T2-5@gated-at.bofh.it> <tkWfg-1T2-37@gated-at.bofh.it>
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On 03/14, Peter Zijlstra wrote:
>
> Do we want a WARN_ON_ONCE(atomic_read(&tsk->usage)); in free_task()?
> Because in the above scenario we're freeing it with references on.

Not sure, in this case copy_process() should decrement tsk->usage
before free_task(), note the atomic_set(&tsk->usage, 2) in
dup_task_struct().

Perhaps we should just add WARN_ON(tsk->usage != 2) into copy_process()
right before free_task() ?

On the other hand, WARN_ON(atomic_read(&tsk->usage)) looks pointless,
the only caller is put_task_struct().

Oleg.

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Thread

Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 14:00 +0100
  Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-14 14:30 +0100
    Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 14:50 +0100
  Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-14 15:10 +0100
    Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 15:10 +0100
      Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-14 15:40 +0100
        Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 16:10 +0100
          Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 16:10 +0100
            Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-14 16:40 +0100
              Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 16:50 +0100
          Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 16:30 +0100
            Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-14 18:40 +0100
              Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-15 17:50 +0100
                Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-16 13:10 +0100
                Re: perf: use-after-free in perf_release Peter Zijlstra <peterz@infradead.org> - 2017-03-16 15:00 +0100
                Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-16 17:50 +0100
          Re: perf: use-after-free in perf_release Oleg Nesterov <oleg@redhat.com> - 2017-03-14 16:30 +0100

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