Re: [PATCH v2] tracing/uprobe: Add missing PID filter for uretprobe

[Oleg Nesterov <oleg@redhat.com>]

On 08/27, Jiri Olsa wrote:
>
> On Tue, Aug 27, 2024 at 12:08:39PM +0200, Jiri Olsa wrote:
> > >
> > > 	-	if (link->task && current->mm != link->task->mm)
> > > 	+	if (link->task && !same_thread_group(current, link->task))
> > >
> > > in uprobe_prog_run() to make "filter by *process*" true, but this won't
> > > fix the problem with link->task->mm == NULL in uprobe_multi_link_filter().
> >
> > would the same_thread_group(current, link->task) work in such case?
> > (zombie leader with other alive threads)
>
> should uprobe_perf_filter use same_thread_group as well instead
> of mm pointers check?

uprobe_perf_filter or uprobe_multi_link_filter ?

In any case I don't think same_thread_group(current, whatever) can work.

For example, uc->filter() can be called from uprobe_register() paths. In
this case "current" is the unrelated task which does, say, perf-record, etc.
Even if uc->filter() was only called from handler_chain(), it couldn't work,
think of UPROBE_HANDLER_REMOVE.

See also another email I sent a minute ago.

Oleg.