linux-kernel - Re: [GIT PULL] ucounts: Count rlimits in each user namespace

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Message-ID: <CAHk-=wj1z-NKxedgZvSS37iH=EKE47PkL=+BYccAUtsuB1sySQ@mail.gmail.com>
Date:   Mon, 28 Jun 2021 20:47:12 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Alexey Gladkov <legion@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux.dev>
Subject: Re: [GIT PULL] ucounts: Count rlimits in each user namespace

On Mon, Jun 28, 2021 at 3:35 PM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> This is the work mainly by Alexey Gladkov to limit rlimits to the
> rlimits of the user that created a user namespace, and to allow users to
> have stricter limits on the resources created within a user namespace.

I guess all the performance issues got sorted, since I haven't seen
any reports from the test robots.

I do end up with two questions, mainly because of looking at the
result of the conflict resolution.

In particular, in __sigqueue_alloc(), two oddities..

Why the "sigpending < LONG_MAX" test in that

        if (override_rlimit || (sigpending < LONG_MAX && sigpending <=
task_rlimit(t, RLIMIT_SIGPENDING))) {

thing?

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()..)

Hmm?

And somebody should verify that I didn't screw anything up in my merge
resolution. It all looked very straightforward, but mistakes happen..

                   Linus