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Date: Mon, 9 Apr 2018 13:40:34 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>,
        Ingo Molnar <mingo@redhat.com>, Steven Rostedt <rostedt@goodmis.org>,
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        Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
        linux-kernel@vger.kernel.org
Subject: Re: uprobes/perf: KASAN: use-after-free in uprobe_perf_close
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On Mon, Apr 09, 2018 at 12:40:10PM +0200, Oleg Nesterov wrote:
> But I still think that we should (try to) remove put_task_struct() from put_ctx().
> 
> Quite possibly I missed something, but I think it only adds some confusion. Once
> again, even if ctx can't go away you can't use ctx->task without TASK_TOMBSTONE
> check, exactly because this task can exit. So why perf_event_context should add
> another reference?

Ah, I see what you mean. Yes that might be possible.