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From: Andrew Vagin on 15 May 2010 10:20
On 05/14/2010 10:48 PM, Oleg Nesterov wrote:
> On 05/14, Stanislaw Gruszka wrote:
>
>> On Fri, 14 May 2010 18:03:57 +0200
>> Oleg Nesterov<oleg(a)redhat.com> wrote:
>>
>>
>>> On 05/14, Andrey Vagin wrote:
>>>
>>>> @@ -613,6 +613,8 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
>>>> * and may cease to exist at any time. Don't use or modify
>>>> * new_timer after the unlock call.
>>>> */
>>>> +out_cleanup:
>>>> + CLOCK_DISPATCH(new_timer->it_clock, timer_cleanup, (new_timer));
>>>>
>>> But at first glance you are right, posix_cpu_timer_create() does
>>> get_task_struct(it.cpu.task).
>>>
>> If I understand problem correctly, seems to be fine to move
>> CLOCK_DISPATCH(which_clock, timer_create, (new_timer));
>> after all possible EFAULT errors and solve leak without creating
>> new timer_cleanup() callback.
>>
> I thought about this too, we are doing copy_to_user(created_timer_id)
> "in advance" anyway. Probably we can move all this code block
>
> new_timer->it_id = (timer_t) new_timer_id;
> new_timer->it_clock = which_clock;
> new_timer->it_overrun = -1;
> error = CLOCK_DISPATCH(which_clock, timer_create, (new_timer));
> if (error)
> goto out;
>
> down, right before we take ->siglock.
>
You are right. I will send a new patch sooner. Thanks for your comments.
> But I don't understand the change in posix_cpu_timer_del() from 1/2.
>
timer_cleanup doesn't do the disarm timer. In case fail in timer_create
it's enough to call timer_cleanup. This changes are not necessary in new
version.
>
> Otoh, currently "The next step is hard to back out if there is an error"
> comment is not right, release_posix_timer() does put_pid(). We can
> move copy_to_user(created_timer_id) down after "if (timer_event_spec)"
> block too. (but before CLOCK_DISPATCH(), of course).
>
> Andrey, what do you think?
>
I've look at code again and think that you are right. At first I created
patches for 2.6.18 kernel, more complex code in this place and the
comment "the next step is ..." induced me to make callback timer_cleanup.
> Oleg.
>
>

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