linux-kernel - Re: [PATCH] kernel: auditfilter: looping issue, memory leak if has 2 or more AUDIT

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Date:	Wed, 17 Apr 2013 10:41:07 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Eric Paris <eparis@...hat.com>
CC:	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel: auditfilter: looping issue, memory leak if has
 2 or more AUDIT_FILTERKEYs

On 2013年04月16日 18:38, Chen Gang wrote:
> On 2013年04月16日 18:25, Chen Gang wrote:
>> On 2013年04月12日 17:42, Chen Gang wrote:
>>> On 2013年04月11日 12:10, Chen Gang wrote:
>>>> On 2013年04月11日 05:19, Eric Paris wrote:
>>>>> ----- Original Message -----
>>>>>
>>>>>>>   b. has an new issue for AUDIT_DIR:
>>>>>>>        after AUDIT_DIR succeed, it will set rule->tree.
>>>>>>>        next, the other case fail, then will call audit_free_rule.
>>>>>>>        but audit_free_rule will not free rule->tree.
>>>>> Definitely a couple of leaks here...
>>>>>
>>>>> I'm seeing leaks on size 8, 64, and 128.
>>>>>
>>>>> Al, what do you think?  Should I be calling audit_put_tree() in the error case if entry->tree != NULL?  The audit trees are some of the most complex code in the kernel I think.
>>>>>
>>>>>

  after the test, the original version really has memory leak.

  test:
    the related monitor command is:
      watch -d -n 1 "cat /proc/meminfo | awk '{print \$2}' \
        | head -n 4 | xargs \
        | awk '{print \"used \",\$1 - \$2 - \$3 - \$4}'"
    I run 15 processes of modified auditctl at the same time.

  result:
    for original version:
      can see the memory leak, it will be more clear after 1 - 2 hours.

    for new version (fix it):
      can not see the memory leak after ran 12 - 14 hours.


  I will use LTP (ltp-full-20130109) to test audit again under fedora 17
x86_64 for next-20130415, then send related patch.


  welcome any suggestions or completions.


> 
>   oh, also need buffering optarg of auditctl under fedora 17.
>   or "-F auid=-1" will be truncated to "-F auid".
>   it is ok if not looping again. but in our case, we need loop again.
> 
>   to see memory usage, I think:
>     in top, really used memory = 'used' - 'cached'
>     it is enough for us.
> 
>   welcome any suggestions or completions.
> 
>   thanks.
> 
> 
>>
>>   I am just testing about it with:
>>
>> ---
>> while(1)
>>     auditctl -a exit,always -w /etc -F auid=-1
>> ---
>>
>>   under fedora 17, we need modify the auditctl source code:
>>     a. let -w /etc can pass auditctl checking.
>>     b. let loop infinitely in a process (if process quit, will free mem)
>>     c. need fix a bug for auditctl (under Fedora 17)
>>          audit_open may open 2 times.
>>          when loop infinitely, it will cause resource handle leak.
>>
>>   I have checked (by insert printf in kernel/auditfilter.c):
>>     after modify the auditct, the work flow is just what we want to be.
>>       (will alloc watch, alloc tree, then failure occurs)
>>
>>
>>   I guess, we need 2-3 days to get a test result.
>>
>>
>>   welcome any suggestions and completions.
>>
>>   thanks.
>>
>>
>>
>>>
>>>   it seems, your way is the only executable way (if not change code much).
>>>   what my original idea is incorrect.
>>>
>>>     we need add related code at failure process area in audit_data_to_entry.
>>>     and another functions need not add these code (should not add).
>>>     'watch' also need be processed, since audit_to_watch let ref count = 2.
>>>       (it just like the function audit_del_rule has done)
>>>
>>>   please help check thanks.
>>>
>>>   :-)
>>>
>>>
>>> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
>>> index 81f63f9..f5327ce 100644
>>> --- a/kernel/auditfilter.c
>>> +++ b/kernel/auditfilter.c
>>> @@ -594,6 +594,10 @@ exit_nofree:
>>>  	return entry;
>>>  
>>>  exit_free:
>>> +	if (entry->rule.watch)
>>> +		audit_put_watch(entry->rule.watch); /* matches initial get */
>>> +	if (entry->rule.tree)
>>> +		audit_put_tree(entry->rule.tree); /* that's the temporary one */
>>>  	audit_free_rule(entry);
>>>  	return ERR_PTR(err);
>>>  }
>>>
>>>
>>>
>>>>
>>>>   can we add it in audit_free_rule ?
>>>>
>>>>   maybe like this:
>>>>
>>>> @@ -75,6 +75,8 @@ static inline void audit_free_rule(struct audit_entry *e)
>>>>  	/* some rules don't have associated watches */
>>>>  	if (erule->watch)
>>>>  		audit_put_watch(erule->watch);
>>>> +	if (erule->tree)
>>>> +		audit_put_tree(erule->tree);
>>>>  	if (erule->fields)
>>>>  		for (i = 0; i < erule->field_count; i++) {
>>>>  			struct audit_field *f = &erule->fields[i];
>>>>
>>>>
>>>>   thanks.
>>>>
>>>>   :-)
>>>>
>>>
>>>
>>
>>
> 
> 


-- 
Chen Gang

Asianux Corporation
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