linux-kernel - [PATCH v1.2 0/5] IMA: making i_readcount a first class inode citizen (reposting)

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Message-Id: <1290121382-4039-1-git-send-email-zohar@linux.vnet.ibm.com>
Date:	Thu, 18 Nov 2010 18:02:57 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, jmorris@...ei.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	eparis@...hat.com, viro@...iv.linux.org.uk,
	Dave Chinner <david@...morbit.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	David Safford <safford@...son.ibm.com>
Subject: [PATCH v1.2 0/5] IMA: making i_readcount a first class inode citizen (reposting)

Reposting unchanged, but with Eric's Ack and suggestion. 

This patchset separates the incrementing/decrementing of the i_readcount, in
the VFS layer, from other IMA functionality, by replacing the current
ima_counts_get() call with i_readcount_inc(). Its unclear whether this call to
increment i_readcount should be made earlier, like i_writecount.  Currently the
call is situated immediately after the switch from put_filp() to fput() for
cleanup.

The patch ordering is a bit redundant in order to leave removing the ifdef
around i_readcount until the last patch. The first four patches: redefines
i_readcount as atomic, defines i_readcount_inc/dec(), moves the IMA
functionality in ima_counts_get() to ima_file_check(), and removes the IMA
imbalance code, simplifying IMA. The last patch removes the ifdef around
i_readcount, making i_readcount into a "first class inode citizen".

The generic_setlease code could then take advantage of i_readcount to help
eliminate some of the race conditions, but not all. For now, Eric suggested
upstreaming patches 1-4 and leaving the 5th patch until there is a second user.
Then we can either unconditionally compile it in, or we can wrap it in
something that either user can select in the Kconfig.  Both Bruce and I agree
with his suggestion.

Changelog:
- renamed iget/iput_readcount to i_readcount_inc/dec (Dave Chinner's suggestion)
- finished cleaning up the locking, so that: (based on Eric's comment.)
	- i_lock is not required
	- i_mutex is taken when making measurement decisions to prevent
	  file metadata(eg. permissions, xattr) changing from under it.
	- iint->mutex is taken when accessing/modifying the iint structure.
- Based on the previous posting discussion, i_readcount is now defined as
atomic. 

Mimi

Mimi Zohar (5):
  IMA: convert i_readcount to atomic
  IMA: define readcount functions
  IMA: maintain i_readcount in the VFS layer
  IMA: remove IMA imbalance checking
  IMA: making i_readcount a first class inode citizen

 fs/file_table.c                   |    5 +-
 fs/open.c                         |    3 +-
 include/linux/fs.h                |   16 ++++-
 include/linux/ima.h               |    6 --
 security/integrity/ima/ima_iint.c |    5 --
 security/integrity/ima/ima_main.c |  130 ++++---------------------------------
 6 files changed, 31 insertions(+), 134 deletions(-)

-- 
1.7.2.2

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