linux-kernel - Re: [PATCH v2] kernel: audit_tree: resource management: need put

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Date:	Fri, 10 May 2013 10:08:14 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Eric Paris <eparis@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kernel: audit_tree: resource management: need put_tree
 and goto Err when failure occures

On 05/10/2013 04:11 AM, Andrew Morton wrote:
>> > But we need let 'rule->tree = NULL;' firstly, so can protect rule itself freed in kill_rules().
> I'll believe you ;) I turned this into a proper patch and added your
> (missed) Signed-off-by:.
> 

Thanks.

At least, let 'rule->tree = NULL;' can:

  a. it matches 'rule->tree = tree;' which is before successful return.
       also can make 'if (list_empty(&rule->rlist))' reasonable.

  b. protect rule itself freed in kill_rules(), if it could happen.
       just like all 'rule->tree = NULL;' in audit_remove_tree_rule().

  c. it will no negative effect.


>> > For me, after 'rule->tree = NULL', all things seems fine !!
> Well, what was wrong before?  Is there some user-triggerable
> misbehaviour which you observed?  If so, please describe it.
> 
> 
> 

I think, it will cause issue (randomly): if when we are using auditctl
to add rule to monitor one file, and at the same time, the other user is
just deleting this file.

I guess, it is why original code need 'if (list_empty(&rule->rlist))'
after lock 'audit_filter_mutex' again.

Currently, I am just testing for it (and should give a test), and I will
send the test plan and test result within this week (2013-05-12).


Thanks.

-- 
Chen Gang

Asianux Corporation
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