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

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Date:	Sat, 26 Apr 2014 19:54:47 +0300
From:	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Oleg Nesterov <oleg@...hat.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>,
	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 26 April 2014 16:56, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Sat, Apr 26, 2014 at 11:58:45AM +0300, Dmitry Kasatkin wrote:
>
>> Conflict with Apparmor means with Ubuntu.
>>
>> But answering to your early question..
>> IMA does not want permission denied when measuring and re-measuring files.
>> may_open() is doing that job before.
>>
>> We need quickly introduce kernel_read without LSM checks...
>
> *snarl*
>
> What we need quickly is to introduce you to a textbook or two.  As the
> matter of fact, in this case even wikipedia might suffice...
>

Hopefully we have you who were introduced to a textbook or two about relevant
subject and able kindly help us with the solution instead of telling
me this crap...


> Please, figure out what "mandatory locking" is about, what kind of
> exclusion does it provide and how much is it (un)related to LSM.
>

I admit, I missed this issue, but see above, we have you :)


> It has nothing to do with permission being denied; the normal behaviour is
> to *block* until the lock has been removed.  Or failure with -EAGAIN if
> the file had been opened with O_NDELAY.
>
> The effects apply only to read/write and their ilk; they have nothing
> to do with e.g. O_RDWR open().  And having a file already opened r/w
> by somebody does not prevent another process from opening it and acquiring
> an exclusive lock on some range.


-- 
Thanks,
Dmitry
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