linux-kernel - Re: [PATCH] block: fix memory leak in bio

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Message-ID: <49B4E2BA.3030809@cn.fujitsu.com>
Date:	Mon, 09 Mar 2009 17:34:50 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	LKML <linux-kernel@...r.kernel.org>, martin.petersen@...cle.com
Subject: Re: [PATCH] block: fix memory leak in bio_clone()

Jens Axboe wrote:
> On Mon, Mar 09 2009, Li Zefan wrote:
>> If bio_integrity_clone() fails, bio_clone() returns NULL without freeing
>> the newly allocated bio.
>>
>> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
>> ---
>>  fs/bio.c |    4 +++-
>>  1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/bio.c b/fs/bio.c
>> index 124b95c..896330e 100644
>> --- a/fs/bio.c
>> +++ b/fs/bio.c
>> @@ -465,8 +465,10 @@ struct bio *bio_clone(struct bio *bio, gfp_t gfp_mask)
>>  
>>  		ret = bio_integrity_clone(b, bio, fs_bio_set);
>>  
>> -		if (ret < 0)
>> +		if (ret < 0) {
>> +			bio_put(bio);
>>  			return NULL;
>> +		}
>>  	}
>>  
>>  	return b;
>> -- 1.5.4.rc3 
> 
> Good spotting. But it looks like there are actually several problems
> there. bio_integrity_clone() is mempool backed. Currently that ret < 0
> can never trigger, since bio_integrity_clone() has hard-wired __GFP_WAIT

Do you mean GFP_NOIO? 

> as the mempool mask. So the leak will not occur, but it does mean that
> it isn't honoring the gfp_mask passed in to bio_clone(), which is the

I noticed there was a patch to do this, and seems you planed to merge
it into .29?

"[PATCH] Add gfp_mask to bio_integrity_clone()"

http://lkml.org/lkml/2008/10/30/11

> first bug. The second bug is that it should be using its own bioset, as
> it is illegal to do multiple __GFP_WAIT allocations on a single mempool
> and always expect progress.
> 

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