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

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Date:	Sat, 10 May 2014 01:01:27 +0900
From:	"J. R. Okajima" <hooanon05g@...il.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.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)


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.


J. R. Okajima
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