Re: Fw: 2.5.61 oops running SDET

Linus Torvalds
2003-02-16T01:29:02Z

On Sat, 15 Feb 2003, Andrew Morton wrote:
>
> The recent change to fs/proc/array.c:task_sig()?
>
> buffer += sprintf(buffer, "ShdPnd:\t");
> buffer = render_sigset_t(&p->signal->shared_pending.signal, buffer);

Yeah, but I think the bug has existed for much longer.

It looks like "proc_pid_status()" doesn't actually lock the task at all,
nor even bother to test whether the task has signal state. Which has
_always_ been a bug. I don't know why it would start happening now, but it
might just be unlucky timing.

I think the proper fix is to put a

task_lock()
..
task_unlock()

around the whole proc_pid_status() function, _and_ then verify that
"tsk->sighand" is non-NULL.

(Oh, careful, that's already what "get_task_mm()" does internally, so look
out for deadlocks - you'd need to open-code the get_task_mm() in there
too, so the end result is something like

task_lock(task)
if (task->mm) {
.. mm state
}
if (task->sighand) {
.. signal state
}
..
task_unlock(task);

instead).

Linus