* [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP_STOPPED check
@ 2009-02-13 10:54 Oleg Nesterov
2009-02-20 3:49 ` Roland McGrath
0 siblings, 1 reply; 3+ messages in thread
From: Oleg Nesterov @ 2009-02-13 10:54 UTC (permalink / raw)
To: Andrew Morton
Cc: Jerome Marchand, Roland McGrath, Denys Vlasenko, linux-kernel
This bug is ancient too. ptrace_untrace() must not resume the task
if the group stop in progress, we should set TASK_STOPPED instead.
Unfortunately, we still have problems here:
- if the process/thread was traced, SIGNAL_STOP_STOPPED
does not necessary means this thread group is stopped.
- ptrace breaks the bookkeeping of ->group_stop_count.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
--- 6.29-rc3/kernel/ptrace.c~2_FIX_STOPPED 2009-02-13 11:06:56.000000000 +0100
+++ 6.29-rc3/kernel/ptrace.c 2009-02-13 11:38:50.000000000 +0100
@@ -60,11 +60,15 @@ static void ptrace_untrace(struct task_s
{
spin_lock(&child->sighand->siglock);
if (task_is_traced(child)) {
- if (child->signal->flags & SIGNAL_STOP_STOPPED) {
+ /*
+ * If the group stop is completed or in progress,
+ * this thread was already counted as stopped.
+ */
+ if (child->signal->flags & SIGNAL_STOP_STOPPED ||
+ child->signal->group_stop_count)
__set_task_state(child, TASK_STOPPED);
- } else {
+ else
signal_wake_up(child, 1);
- }
}
spin_unlock(&child->sighand->siglock);
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP_STOPPED check
2009-02-13 10:54 [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP_STOPPED check Oleg Nesterov
@ 2009-02-20 3:49 ` Roland McGrath
2009-02-20 19:13 ` Oleg Nesterov
0 siblings, 1 reply; 3+ messages in thread
From: Roland McGrath @ 2009-02-20 3:49 UTC (permalink / raw)
To: Oleg Nesterov
Cc: Andrew Morton, Jerome Marchand, Denys Vlasenko, linux-kernel
> This bug is ancient too. ptrace_untrace() must not resume the task
> if the group stop in progress, we should set TASK_STOPPED instead.
Right, the change looks correct.
> Unfortunately, we still have problems here:
>
> - if the process/thread was traced, SIGNAL_STOP_STOPPED
> does not necessary means this thread group is stopped.
>
> - ptrace breaks the bookkeeping of ->group_stop_count.
Neither of these should be true today as I understand the code. So if you
have reason to think these, I must be missing something that is likely to
be relevant to reviewing this change.
Thanks,
Roland
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP_STOPPED check
2009-02-20 3:49 ` Roland McGrath
@ 2009-02-20 19:13 ` Oleg Nesterov
0 siblings, 0 replies; 3+ messages in thread
From: Oleg Nesterov @ 2009-02-20 19:13 UTC (permalink / raw)
To: Roland McGrath
Cc: Andrew Morton, Jerome Marchand, Denys Vlasenko, linux-kernel
On 02/19, Roland McGrath wrote:
>
> > This bug is ancient too. ptrace_untrace() must not resume the task
> > if the group stop in progress, we should set TASK_STOPPED instead.
>
> Right, the change looks correct.
>
> > Unfortunately, we still have problems here:
> >
> > - if the process/thread was traced, SIGNAL_STOP_STOPPED
> > does not necessary means this thread group is stopped.
> >
> > - ptrace breaks the bookkeeping of ->group_stop_count.
>
> Neither of these should be true today as I understand the code.
Suppose we have
int main(void)
{
kill(getpid(), SIGSTOP);
for (;;)
;
}
If you strace this task nobody clears SIGNAL_STOP_STOPPED.
As for bookkeeping of ->group_stop_count, I think ptrace_stop() is wrong
in many ways. For example, it decrements ->group_stop_count but doesn't
set SIGNAL_STOP_STOPPED if it becomes zero.
Oleg.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-02-20 19:16 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2009-02-13 10:54 [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP_STOPPED check Oleg Nesterov
2009-02-20 3:49 ` Roland McGrath
2009-02-20 19:13 ` Oleg Nesterov
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