linux-kernel - Re: [RFC 00/12] module: avoid userspace pressure on unwanted allocations

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Message-ID: <c0b2d9d0-ef5e-8c46-109e-742dbec8a07b@redhat.com>
Date:   Mon, 20 Mar 2023 22:15:23 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        pmladek@...e.com, petr.pavlu@...e.com, prarit@...hat.com,
        christophe.leroy@...roup.eu, song@...nel.org,
        torvalds@...ux-foundation.org
Subject: Re: [RFC 00/12] module: avoid userspace pressure on unwanted
 allocations

On 20.03.23 22:09, Luis Chamberlain wrote:
> On Mon, Mar 20, 2023 at 08:40:07PM +0100, David Hildenbrand wrote:
>> On 20.03.23 10:38, David Hildenbrand wrote:
>>> On 18.03.23 01:11, Luis Chamberlain wrote:
>>>> On Thu, Mar 16, 2023 at 04:56:56PM -0700, Luis Chamberlain wrote:
>>>>> On Thu, Mar 16, 2023 at 04:55:31PM -0700, Luis Chamberlain wrote:
>>>>>> On Wed, Mar 15, 2023 at 05:41:53PM +0100, David Hildenbrand wrote:
>>>>>>> I expect to have a machine (with a crazy number of CPUs/devices) available
>>>>>>> in a couple of days (1-2), so no need to rush.
>>>>>>>
>>>>>>> The original machine I was able to reproduce with is blocked for a little
>>>>>>> bit longer; so I hope the alternative I looked up will similarly trigger the
>>>>>>> issue easily.
>>>>>>
>>>>>> OK give this a spin:
>>>>>>
>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230316-module-alloc-opts
>>>>
>>>> Today I am up to here:
>>>>
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230317-module-alloc-opts
>>>>
>>>> The last patch really would have no justification yet at all unless it
>>>> does help your case.
>>>
>>> Still waiting on the system (the replacement system I was able to grab
>>> broke ...).
>>>
>>> I'll let you know once I succeeded in reproducing + testing your fixes.
>>
>> Okay, I have a system where I can reproduce.
>>
>> Should I give
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230319-module-alloc-opts
>>
>> from yesterday a churn?
> 
> Yes please give that a run.

Reproduced with v6.3.0-rc1 (on 1st try)

Not able to reproduce with 20230319-module-alloc-opts so far (2 tries).

> 
> Please collect systemd-analyze given lack of any other tool to evaluate
> any deltas. Can't think of anything else to gather other than seeing if
> it booted.

Issue is that some services (kdump, tuned) seem to take sometimes ages 
on that system to start for some reason, and systemd-analyze refuses to 
do something reasonable while the system is still booting up.

I'll see if I can come up with some data.

> 
> If that boots works then try removing the last patch "module: add a
> sanity check prior to allowing kernel module auto-loading" to see if
> that last patch helped or was just noise. As it stands I'm not convinced
> yet if it did help, if it *does* help we probably need to rethink some
> finit_module() allocations things.

Okay, will try without the last patch tomorrow.

-- 
Thanks,

David / dhildenb