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From: Dmitry Vyukov <dvyukov@google.com>
Date: Tue, 7 Mar 2017 15:17:34 +0100
Message-ID: <CACT4Y+bzNOrMHmfP_cv3Jzaqs0zB3qHY9eu0y4JdKvVw0mgveA@mail.gmail.com>
Subject: Re: perf: use-after-free in perf_release
To: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        syzkaller <syzkaller@googlegroups.com>
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On Tue, Mar 7, 2017 at 3:04 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 03/06, Peter Zijlstra wrote:
>>
>> and this is a failed fork().
>>
>>
>> However, inherited events don't have a filedesc to fput(), and
>> similarly, a task that fails for has never been visible to attach a perf
>> event to because it never hits the pid-hash.
>
> Yes, it is not visible to find_task_by_vpid() until copy_process() does
> attach_pid(PIDTYPE_PID), and copy_process() can't fail after that.


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?