linux-kernel - Re: IMA + O_DIRECT (Re: [PATCH 0/1] fix IMA + Apparmor kernel panic)

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Date:	Fri, 09 May 2014 15:44:59 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	"J. R. Okajima" <hooanon05g@...il.com>
Cc:	Dmitry Kasatkin <d.kasatkin@...sung.com>, viro@...iv.linux.org.uk,
	ebiederm@...ssion.com, linux-security-module@...r.kernel.org,
	eparis@...hat.com, dmitry.kasatkin@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: IMA + O_DIRECT (Re: [PATCH 0/1] fix IMA + Apparmor kernel panic)

On Sat, 2014-05-10 at 01:01 +0900, J. R. Okajima wrote: 
> Mimi Zohar:
> > Another approach was posted here
> > http://marc.info/?l=linux-security-module&m=138919062430367&w=2 which
> > also was not upstreamed.
> 
> It might be better a little than previous one which handles the flag
> temporarily. But, in order to make the code cleaner particulary for
> do_blockdev_direct_IO(), I'd suggest
> - make two new static inline functions like
>   r = ima_aware_file_inode_mutex_lock(file) and ..._unlock(r, file).
> - these new functions are complied when CONFIG_IMA is enabled, otherwise
>   they are plain mutex_lock/unlock().
> - then do_blockdev_direct_IO() can call them blindly.
> - of course, O_DIRECT_HAVELOCK should be complied only when CONFIG_IMA
>   is enabled too.
> 
> I can guess that several people thinks that is still "ugly locking", but
> the deadlock is much ugly in real world. And we need some workaround for
> it.

I assume so, as there wasn't any comment.  As a temporary fix, would it
make sense not to measure/appraise/audit files opened with the direct-io
flag based policy?  Define a new IMA policy option 'directio'.  A sample
rule would look like:  

dont_appraise bprm_check directio fsuuid=... 

Mimi

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