linux-kernel - Re: [PATCH v11 5/9] Reimplement RLIMIT

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Message-ID: <20210818131117.x7omzb2wkjq7le3s@example.org>
Date:   Wed, 18 Aug 2021 15:11:17 +0200
From:   Alexey Gladkov <legion@...nel.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     "Ma, XinjianX" <xinjianx.ma@...el.com>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        lkp <lkp@...el.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "christian.brauner@...ntu.com" <christian.brauner@...ntu.com>,
        "containers@...ts.linux-foundation.org" 
        <containers@...ts.linux-foundation.org>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

On Tue, Aug 17, 2021 at 10:47:14AM -0500, Eric W. Biederman wrote:
> "Ma, XinjianX" <xinjianx.ma@...el.com> writes:
> 
> > Hi Alexey,
> >
> > When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
> > in kselftest failed with following message.
> 
> Which kernel was this run against?
> 
> Where can the mq_perf_tests that you ran and had problems with be found?
> 
> During your run were you using user namespaces as part of your test
> environment?
> 
> The error message too many files corresponds to the error code EMFILES
> which is the error code that is returned when the rlimit is reached.
> 
> One possibility is that your test environment was run in a user
> namespace and so you wound up limited by rlimit of the user who created
> the user namespace at the point of user namespace creation. 
> 
> At this point if you can give us enough information to look into this
> and attempt to reproduce it that would be appreciated.

I was able to reproduce it on master without using user namespace.
I suspect that the maximum value is not assigned here [1]:

set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/fork.c#n832

> > If you confirm and fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot lkp@...el.com
> >
> > ```
> > # selftests: mqueue: mq_perf_tests
> > #
> > # Initial system state:
> > #       Using queue path:                       /mq_perf_tests
> > #       RLIMIT_MSGQUEUE(soft):                  819200
> > #       RLIMIT_MSGQUEUE(hard):                  819200
> > #       Maximum Message Size:                   8192
> > #       Maximum Queue Size:                     10
> > #       Nice value:                             0
> > #
> > # Adjusted system state for testing:
> > #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> > #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> > #       Maximum Message Size:                   16777216
> > #       Maximum Queue Size:                     65530
> > #       Nice value:                             -20
> > #       Continuous mode:                        (disabled)
> > #       CPUs to pin:                            3
> > # ./mq_perf_tests: mq_open() at 296: Too many open files
> > not ok 2 selftests: mqueue: mq_perf_tests # exit=1
> > ```    
> >
> > Test env:
> > rootfs: debian-10
> > gcc version: 9
> >
> > ------
> > Thanks 
> > Ma Xinjian
> 
> Eric
> 

-- 
Rgrds, legion