linux-kernel - Re: [PATCH] ptrace: make former thread ID available via PTRACE_GETEVENTMSG after PTRACE_EVENT

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Date:	Tue, 28 Jun 2011 02:31:08 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ptrace: make former thread ID available via
 PTRACE_GETEVENTMSG after PTRACE_EVENT_EXEC stop (v.2)

On Sun, Jun 26, 2011 at 10:04 PM, Oleg Nesterov <oleg@...hat.com> wrote:
>> +                     pid_t old_pid = old_pid; /* for compiler */
>
> we have uninitialized_var() for this,
>
>        pid_t uninitialized_var(old_pid);
>
>> -                     retval = fn(bprm, regs);
>> +                     if (task_ptrace(current) & PT_PTRACED) {
>
> May be PT_TRACE_EXEC makes more sense. Note that ptrace_event_enabled() was
> recently added.
>
>> +                             /* Need to fetch pid before load_binary changes it */
>> +                             rcu_read_lock();
>> +                             old_pid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
>
> OK, this looks correct. But imho this code looks strange inside the
> for (;;) loop. Perhaps it would be more clean to record the old pid
> before.
>
>>                               if (depth == 0)
>> -                                     tracehook_report_exec(fmt, bprm, regs);
>> +                                     tracehook_report_exec(fmt, bprm, regs, old_pid);
>
> Heh, you are out of luck ;) This hook was already killed. Please redo
> against git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc.git ptrace

I just sent rediffed version against this branch as a separate mail.

I think I addressed all your concerns in it.

-- 
vda
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