linux-kernel - Re: perf: use-after-free in perf

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Message-ID: <CACT4Y+YNwcjebv9yK3S8xGcLqbrqq+Cb3+zbJWMnoinpt82dtg@mail.gmail.com>
Date:   Mon, 6 Mar 2017 13:27:41 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: perf: use-after-free in perf_release

On Mon, Mar 6, 2017 at 1:23 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Mar 06, 2017 at 01:17:42PM +0100, Dmitry Vyukov wrote:
>> On Mon, Mar 6, 2017 at 1:13 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> > On Mon, Mar 06, 2017 at 10:57:07AM +0100, Dmitry Vyukov wrote:
>> >> Hello,
>> >>
>> >> I've got the following use-after-free report while running syzkaller
>> >> fuzzer on 86292b33d4b79ee03e2f43ea0381ef85f077c760. Note that the task
>> >> is freed right in copy_process due to some error, but it's referenced
>> >> by another thread in perf subsystem.
>> >
>> > Weird... you don't happen to have a reproduction case available?
>>
>>
>> Unfortunately no. I've looked at both logs that I have and there are
>> no memory allocation failures preceding the crash (however maybe
>> somebody used NOWARN?). But probably if you inject an error into
>> copy_process somewhere after perf_event_init_task, it should reproduce
>> the bug with KASAN I think.
>
> I'll try. Thanks!


I think you will also need the attached patch. It seems that it was
found due to it. Going to send it out soon.

View attachment "atomic.patch" of type "text/x-patch" (7088 bytes)