linux-kernel - Re: [PATCH 1/8] ucounts: Fix RLIMIT

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Date:   Mon, 14 Feb 2022 19:37:27 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, Alexey Gladkov <legion@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Solar Designer <solar@...nwall.com>,
        Ran Xiaokai <ran.xiaokai@....com.cn>,
        containers@...ts.linux-foundation.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/8] ucounts: Fix RLIMIT_NPROC regression

On Thu, Feb 10, 2022 at 08:13:17PM -0600, "Eric W. Biederman" <ebiederm@...ssion.com> wrote:
> This can be fixed either by fixing the test or by moving the increment
> to be before the test.  Fix it my moving copy_creds which contains
> the increment before is_ucounts_overlimit.

This is simpler than my approach and I find it correct too.

> Both the test in fork and the test in set_user were semantically
> changed when the code moved to ucounts.  The change of the test in
> fork was bad because it was before the increment.
>
> The test in set_user was wrong and the change to ucounts fixed it.  So
> this fix is only restore the old behavior in one lcatio not two.

Whom should be the task accounted to in the case of set*uid? (The change
to ucounts made the check against the pre-switch user's ucounts.)

> ---
>  kernel/fork.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)

Reviewed-by: Michal Koutný <mkoutny@...e.com>