linux-kernel - Re: fs/block_dev.c:953: warning: 'found' might be used uninitialized in this function

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Message-Id: <46C1CD24-F48E-4EB9-B6A5-E1B3C303C62F@mac.com>
Date:	Thu, 29 Mar 2007 23:16:39 -0400
From:	Kyle Moffett <mrmacman_g4@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jiri Kosina <jikos@...os.cz>, Lee Revell <rlrevell@...-job.com>,
	Toralf Förster <toralf.foerster@....de>,
	andrea@...e.de, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: fs/block_dev.c:953: warning: 'found' might be used uninitialized in this function

On Mar 28, 2007, at 16:14:54, Andrew Morton wrote:
> On Wed, 28 Mar 2007 19:23:32 +0200 (CEST)
> Jiri Kosina <jikos@...os.cz> wrote:
>
>> blockdev: bd_claim_by_kobject() could check value of unititalized  
>> pointer
>>
>> Fixes this warning:
>>
>> fs/block_dev.c: In function `bd_claim_by_kobject':
>> fs/block_dev.c:953: warning: 'found' might be used uninitialized  
>> in this function
>>
>> struct bd_holder *found is initialized only when bd_claim()  
>> returns zero. If it returns nonzero, ptr stays uninitialized.  
>> Later the value of the pointer is checked.
>
> that generates extra code and people get upset.
>
> One approach which we could ue in here is
>
> 	struct bd_holder *found = found;  /* Suppress bogus gcc warning */

Well, that would be correct except the warning is an actual kernel  
bug.  Read Jiri's message (which you also quoted):
> struct bd_holder *found is initialized only when bd_claim() returns  
> zero. If it returns nonzero, ptr stays uninitialized. Later the  
> value of the pointer is checked.

So in this case it has to be initialized to NULL or there's a  
potential BUG() lurking.

Cheers,
Kyle Moffett

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