On Tue, Jun 29, 2021 at 10:18 AM Alexey Gladkov <legion@xxxxxxxxxx> wrote:
>
>
> > And why test for "ucounts" being non-NULL in
> >
> > if (ucounts && dec_rlimit_ucounts(ucounts,
> > UCOUNT_RLIMIT_SIGPENDING, 1))
> > put_ucounts(ucounts);
> >
> > when afaik both of those should be happy with a NULL 'ucounts' pointer
> > (if it was NULL, we certainly already used it for the reverse
> > operations for get_ucounts() and inc_rlimit_ucounts()..)
>
> The get_ucount() can theoretically return NULL. It increments the
> reference counter and if it overflows, the function will return NULL.
.. but my point is that dec_rlimit_ucounts() and put_ucounts() should
be fine with whatever get_ucounts() returned. No
It looks like put_ucounts() is unhappy with a NULL ucounts argument,
but I think _that_ is what should get fixed.
I think that conceptually we should have two clear alternatives:
(a) either "get_ucounts()" returning NULL should be an error, and we
would have returned long before
or
(b) a NULL uncounts is usable, and a sequence like
put_ucounts(get_ucounts()) should just always work.
And honestly, a lot of the other ucounts funcrtions seem to take that
(b) approach. Example in that very function:
ucounts = task_ucounts(t);
sigpending = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING, 1);
which at no point tested for NULL or returned an error.
(And that also implies that the comment in dec_rlimit_ucounts() about
"Silence compiler warning" should just go away, because it's not just
a compiler warning, it's a required initialization).
Linus
