linux-kernel - Re: [TOMOYO 03/15](repost) Memory and pathname management functions.

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Date:	Wed, 3 Oct 2007 20:12:11 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	jmorris@...ei.org
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, chrisw@...s-sol.org
Subject: Re: [TOMOYO 03/15](repost) Memory and pathname management functions.

Hello.

James Morris wrote:
> Would you please explain why you need another level of memory allocation?
> 
> What does it do apart from let you check for memory leaks?

Difference between tmy_alloc() and kmalloc() are

  tmy_alloc() allows administrator know "how much memory is used by TOMOYO Linux modules"
  via /sys/kernel/security/tomoyo/meminfo interface.
  This feature was requested by TOMOYO Linux users.
  /proc/slabinfo can show how much memory is used by all modules,
  but it cannot show how much memory is used by TOMOYO Linux modules.

  tmy_alloc() can indicate memory-leaking bug and can avoid double-kfree() bug
  by keeping the pointer returned by kmalloc() in a local "cache_list" list.

  tmy_alloc() also keeps the size of memory allocated by kmalloc() in "cache_list" list
  so that administrator can know "how much memory is used by TOMOYO Linux modules".
  Calling ksize() after kmalloc() in tmy_alloc() and
  calling ksize() before kfree() in tmy_free() might be better
  if double-kfree-checks and memory-leaking-checks (i.e. "tmy_cachep") are unneeded.

Regards.

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