linux-kernel - Re: [PATCH] dm-zoned: free dmz->ddev array in dmz_put_zoned

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Message-ID: <vdtvo2av3upya6mugjyiqo2hfnn6q4dpofoku6rvrtgmycgbrp@scpcnu3ta7ch>
Date:   Wed, 20 Sep 2023 17:35:56 +0300
From:   Fedor Pchelkin <pchelkin@...ras.ru>
To:     Hannes Reinecke <hare@...e.de>
Cc:     Mike Snitzer <snitzer@...nel.org>,
        Alasdair Kergon <agk@...hat.com>, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: [PATCH] dm-zoned: free dmz->ddev array in dmz_put_zoned_device

On 23/09/20 04:06PM, Hannes Reinecke wrote:
> On 9/20/23 12:51, Fedor Pchelkin wrote:
> > Commit 4dba12881f88 ("dm zoned: support arbitrary number of devices")
> > made the pointers to additional zoned devices to be stored in a
> > dynamically allocated dmz->ddev array. However, this array is not freed.
> > 
> > Free it when cleaning up zoned device information inside
> > dmz_put_zoned_device(). Assigning NULL to dmz->ddev elements doesn't make
> > sense there as they are not supposed to be reused later and the whole dmz
> > target structure is being cleaned anyway.
> > 
> > Found by Linux Verification Center (linuxtesting.org).
> > 
> > Fixes: 4dba12881f88 ("dm zoned: support arbitrary number of devices")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> > ---
> >   drivers/md/dm-zoned-target.c | 8 +++-----
> >   1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c
> > index ad8e670a2f9b..e25cd9db6275 100644
> > --- a/drivers/md/dm-zoned-target.c
> > +++ b/drivers/md/dm-zoned-target.c
> > @@ -753,12 +753,10 @@ static void dmz_put_zoned_device(struct dm_target *ti)
> >   	struct dmz_target *dmz = ti->private;
> >   	int i;
> > -	for (i = 0; i < dmz->nr_ddevs; i++) {
> > -		if (dmz->ddev[i]) {
> > +	for (i = 0; i < dmz->nr_ddevs; i++)
> > +		if (dmz->ddev[i])
> >   			dm_put_device(ti, dmz->ddev[i]);
> > -			dmz->ddev[i] = NULL;
> > -		}
> > -	}
> > +	kfree(dmz->ddev);
> >   }
> >   static int dmz_fixup_devices(struct dm_target *ti)
> 
> Hmm. I'm not that happy with it; dmz_put_zoned_device() is using dm_target
> as an argument, whereas all of the functions surrounding the call sites is
> using the dmz_target directly.
> 
> Mind to modify the function to use 'struct dmz_target' as an argument?

dm_target is required inside dmz_put_zoned_device() for dm_put_device()
calls. I can't see a way for referencing it via dmz_target. Do you mean
passing additional second argument like
  dmz_put_zoned_device(struct dmz_target *dmz, struct dm_target *ti) ?

BTW, I also think it can be renamed to dmz_put_zoned_devices().

> 
> Cheers,
> 
> Hannes
> -- 
> Dr. Hannes Reinecke                Kernel Storage Architect
> hare@...e.de                              +49 911 74053 688
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