On Fri, Oct 22, 2021 at 09:25:02AM -0700, Kees Cook wrote:
> On Fri, Oct 22, 2021 at 05:09:35PM +0200, Peter Zijlstra wrote:
> > /**
> > * stack_trace_save_tsk - Save a task stack trace into a storage array
> > * @task: The task to examine
> > @@ -135,7 +142,6 @@ EXPORT_SYMBOL_GPL(stack_trace_save);
> > unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
> > unsigned int size, unsigned int skipnr)
> > {
> > - stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
> > struct stacktrace_cookie c = {
> > .store = store,
> > .size = size,
> > @@ -143,11 +149,8 @@ unsigned int stack_trace_save_tsk(struct
> > .skip = skipnr + (current == tsk),
> > };
> >
> > - if (!try_get_task_stack(tsk))
> > - return 0;
> > + task_try_func(tsk, try_arch_stack_walk_tsk, &c);
>
> Pardon my thin understanding of the scheduler, but I assume this change
> doesn't mean stack_trace_save_tsk() stops working for "current", right?
> In trying to answer this for myself, I couldn't convince myself what value
> current->__state have here. Is it one of TASK_(UN)INTERRUPTIBLE ?
current really shouldn't be using stack_trace_save_tsk(), and no you're
quite right, it will not work for current, irrespective of ->__state,
current will always be ->on_rq.
I started auditing stack_trace_save_tsk() users a few days ago, but
didn't look for this particular issue. I suppose I'll have to start over
with that.
