linux-kernel - Re: [PATCH 6/6] mqueue: fix mq_open() file descriptor leak on user-space processes

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Date:	Thu, 25 Feb 2010 21:17:15 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Xiaotian Feng <xtfeng@...il.com>
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	André Goddard Rosa <andre.goddard@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Serge E . Hallyn" <serue@...ibm.com>,
	Cedric Le Goater <clg@...ibm.com>,
	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] mqueue: fix mq_open() file descriptor leak on
	user-space processes

On Thu, Feb 25, 2010 at 06:49:09PM +0800, Xiaotian Feng wrote:
>On Thu, Feb 25, 2010 at 2:59 PM, Américo Wang <xiyou.wangcong@...il.com> wrote:
>> On Thu, Feb 25, 2010 at 12:25 PM, Américo Wang <xiyou.wangcong@...il.com> wrote:
>>> On Thu, Feb 25, 2010 at 12:00 PM, Xiaotian Feng <xtfeng@...il.com> wrote:
>>>> 2010/2/25 Américo Wang <xiyou.wangcong@...il.com>:
>>>>> On Tue, Feb 23, 2010 at 3:04 PM, André Goddard Rosa
>>>>> <andre.goddard@...il.com> wrote:
>>>>>> It can be triggered by the following test program:
>>>>>>
>>>>>
>>>>> <snip>
>>>>>
>>>>>>
>>>>>> When not running valgrind, user-space program segfaults trying to execute
>>>>>> strerror(errno). With valgrind, it executes successfully and prints the
>>>>>> 5 open files: stdin, stdout, stderr, pipe[0] and pipe[1].
>>>>>>
>>>>>> Signed-off-by: André Goddard Rosa <andre.goddard@...il.com>
>>>>>> ---
>>>>>
>>>>> The code has more than just this problem, could you please try
>>>>> my patch below?
>>>>>
>>>>> Thanks.
>>>>>
>>>>> ---------------------------->
>>>>>
>>>>> Clean up the failure path of sys_mq_open().
>>>>>
>>>>> Reorder the goto labels;
>>>>> Rename 'upsem' to 'upunlock';
>>>>> Remove some unused labels;
>>>>> Fix some wrong goto path.
>>>>>
>>>>
>>>> I think it's wrong to move dput after mntput
>>>
>>> Oh, this is to say mntget() should be called before lookup_one_len(),
>>> the original code seems wrong again...
>>>
>>
>> How about the one below?
>
>This is definitely wrong,
>
> 	if (IS_ERR(filp)) {
> 		error = PTR_ERR(filp);
>-		goto out_putfd;
>+		goto out;
> 	}
>
>filp is assigned by do_open or do_create in mqueue.c, take a look at
>the code, if do_open/do_create is failed, kernel is already dput &
>mntput...
>

Clearly the original code is a piece of sh*t.

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