From: Linus Torvalds <torvalds@linux-foundation.org>
To: Alexey Gladkov <legion@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Containers <containers@lists.linux.dev>
Subject: Re: [GIT PULL] ucounts: Count rlimits in each user namespace
Date: Tue, 29 Jun 2021 11:07:11 -0700 [thread overview]
Message-ID: <CAHk-=wgcpK3XdFKJ98b_YucXbQMJMgJssAk=sQ-XUo-tyiMjVg@mail.gmail.com> (raw)
In-Reply-To: <20210629171757.shyr222zjpm6ev5t@example.org>
On Tue, Jun 29, 2021 at 10:18 AM Alexey Gladkov <legion@kernel.org> 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
next prev parent reply other threads:[~2021-06-29 18:07 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 22:35 [GIT PULL] ucounts: Count rlimits in each user namespace Eric W. Biederman
2021-06-29 3:47 ` Linus Torvalds
2021-06-29 15:04 ` Eric W. Biederman
2021-06-29 15:51 ` Eric W. Biederman
2021-06-29 16:34 ` Linus Torvalds
2021-06-29 16:42 ` Eric W. Biederman
2021-06-29 17:09 ` Eric W. Biederman
2021-07-01 16:41 ` Alexey Gladkov
2021-07-01 20:05 ` Eric W. Biederman
2021-06-29 17:17 ` Alexey Gladkov
2021-06-29 18:07 ` Linus Torvalds [this message]
2021-06-29 20:20 ` Alexey Gladkov
2021-06-29 20:33 ` Linus Torvalds
2021-06-29 21:22 ` Alexey Gladkov
2021-07-02 17:54 ` [PATCH] ucounts: Fix UCOUNT_RLIMIT_SIGPENDING counter leak Alexey Gladkov
2021-07-02 22:13 ` Linus Torvalds
2021-07-07 16:50 ` Alexey Gladkov
2021-07-07 17:23 ` Linus Torvalds
2021-07-08 10:33 ` [PATCH v2] " Alexey Gladkov
2021-07-08 18:44 ` Linus Torvalds
2021-07-08 11:00 ` [PATCH] ucounts: " Alexey Gladkov
2021-06-29 3:50 ` [GIT PULL] ucounts: Count rlimits in each user namespace pr-tracker-bot
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