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From:   "Eric W. Biederman" <ebiederm@xmission.com>
To:     Michal =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>
Cc:     linux-kernel@vger.kernel.org, Alexey Gladkov <legion@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Solar Designer <solar@openwall.com>,
        Ran Xiaokai <ran.xiaokai@zte.com.cn>,
        containers@lists.linux-foundation.org, stable@vger.kernel.org
References: <87o83e2mbu.fsf@email.froward.int.ebiederm.org>
        <20220211021324.4116773-1-ebiederm@xmission.com>
        <20220214183727.GA10803@blackbody.suse.cz>
Date:   Wed, 16 Feb 2022 09:22:06 -0600
In-Reply-To: <20220214183727.GA10803@blackbody.suse.cz> ("Michal
 =?utf-8?Q?Koutn=C3=BD=22's?=
        message of "Mon, 14 Feb 2022 19:37:27 +0100")
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Subject: Re: [PATCH 1/8] ucounts: Fix RLIMIT_NPROC regression
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Michal Koutný <mkoutny@suse.com> writes:

> On Thu, Feb 10, 2022 at 08:13:17PM -0600, "Eric W. Biederman" <ebiederm@xmission.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.)

It needs to be post-switch in the case of set*id().

I have that fixed in the next version of my patchset.

>> ---
>>  kernel/fork.c | 10 +++++-----
>>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> Reviewed-by: Michal Koutný <mkoutny@suse.com>