linux-kernel - Re: Kernel panic at Ubuntu: IMA + Apparmor

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Message-ID: <CACE9dm9gs64C9JfSYKboUOwT_uXC7Ha1kuXsMWOE-0isQuzfmg@mail.gmail.com>
Date:	Fri, 25 Apr 2014 23:20:54 +0300
From:	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Dmitry Kasatkin <d.kasatkin@...sung.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	John Johansen <john.johansen@...onical.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	James Morris <jmorris@...ei.org>, viro@...iv.linux.org.uk,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kernel-team <kernel-team@...ts.ubuntu.com>
Subject: Re: Kernel panic at Ubuntu: IMA + Apparmor

On 25 April 2014 23:01, Oleg Nesterov <oleg@...hat.com> wrote:
> On 04/25, Eric W. Biederman wrote:
>>
>> Oleg Nesterov <oleg@...hat.com> writes:
>>
>> > Well. I _think_ that __fput() and ima_file_free() in particular should not
>> > depend on current and/or current->nsproxy. If nothing else, fput() can be
>> > called by the unrelated task which looks into /proc/pid/.
>> >
>> > But again, task_work_add() has more and more users, and it seems that even
>> > __fput() paths can do "everything", so perhaps it would be safer to allow
>> > to use ->nsproxy in task_work_run.
>>
>> Like I said, give me a clear motivating case.
>
> I agree, we need a reason. Currently I do not see one.
>
>> Right now not allowing
>> nsproxy is turning up bugs in __fput.  Which seems like a good thing.
>
> This is what I certainly agree with ;)
>

Hi,

IMA uses kernel_read API which does not know anything about caller.
And of course security frameworks are at guard as usual.

Exactly after reading first Eric's respons, I thought why to scratch
the head when task work queues are indeed designed for tasks...

And if you to dig for the history, IMA-appraisal was stuck due to
lockdep reporting even though it was on non-everlaping cases.
IIRC files vs. directories...

After that IIRC Al Viro discussed about delayed fput and IIRC Oleg
(sorry if I am wrong) introduced task work queues.

So IMA-appraisal was able to be upstreamed... That was ~3.4 time frame, IIRC

Name space also dated around ~3.4??
Apparmor namespace change was also around that time.

3.10 introduces this name space order change and broke IMA-appraisal.

Isn't it a clear motivating case???

- Dmitry


> Oleg.
>
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-- 
Thanks,
Dmitry
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