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

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Date:	Mon, 9 Mar 2009 10:38:36 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, martin.petersen@...cle.com
Subject: Re: [PATCH] block: fix memory leak in bio_clone()

On Mon, Mar 09 2009, Li Zefan wrote:
> 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? 

The __GFP_WAIT part of GFP_NOIO is the important bit :-)

> > 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

Hmm strange, apparently that never got queued up and I had forgotten all
about that issue until your email. I'll add it asap.

> > 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.

That one still stands.

-- 
Jens Axboe

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