linux-kernel - Re: [PATCH v4] mtd: spi-nor: fix memory leak when using debugfs

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Date:   Mon, 6 Mar 2023 12:05:58 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Michael Walle <michael@...le.cc>, linux-kernel@...r.kernel.org,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Pratyush Yadav <pratyush@...nel.org>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v4] mtd: spi-nor: fix memory leak when using
 debugfs_lookup()

Hi Greg,

gregkh@...uxfoundation.org wrote on Mon, 6 Mar 2023 10:13:33 +0100:

> On Mon, Mar 06, 2023 at 09:33:36AM +0100, Miquel Raynal wrote:
> > Hi Greg,
> > 
> > gregkh@...uxfoundation.org wrote on Mon, 6 Mar 2023 07:52:38 +0100:
> >   
> > > On Wed, Feb 08, 2023 at 05:15:41PM +0100, Michael Walle wrote:  
> > > > Am 2023-02-08 17:02, schrieb Greg Kroah-Hartman:    
> > > > > When calling debugfs_lookup() the result must have dput() called on it,
> > > > > otherwise the memory will leak over time.  To solve this, remove the
> > > > > lookup and create the directory on the first device found, and then
> > > > > remove it when the module is unloaded.
> > > > > 
> > > > > Cc: Tudor Ambarus <tudor.ambarus@...rochip.com>
> > > > > Cc: Pratyush Yadav <pratyush@...nel.org>
> > > > > Cc: Michael Walle <michael@...le.cc>
> > > > > Cc: Miquel Raynal <miquel.raynal@...tlin.com>
> > > > > Cc: Richard Weinberger <richard@....at>
> > > > > Cc: Vignesh Raghavendra <vigneshr@...com>
> > > > > Cc: linux-mtd@...ts.infradead.org
> > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>    
> > > > 
> > > > Reviewed-by: Michael Walle <michael@...le.cc>
> > > > 
> > > > one nit below I didn't notice earlier, no need to send a new
> > > > patch version just for that.
> > > > 
> > > > ..
> > > >     
> > > > > +void spi_nor_debugfs_shutdown(void)
> > > > > +{
> > > > > +	if (rootdir)
> > > > > +		debugfs_remove(rootdir);    
> > > > 
> > > > debugfs_remove() already has a check for NULL.
> > > >     
> > > 
> > > Ah, good catch, I merged this in when I applied it to my tree, thanks!  
> > 
> > Any reasons why you did apply this patch to your tree? It is a spi-nor
> > fix, I would have expected it to go through mtd.  
> 
> It's been sitting around for a month, I assumed it was lost, so I picked
> it up.

Sorry if it took too long, the merge window also happened during that
time, we are collecting patches now that 6.3-rc1 has been released.
Next time don't hesitate to ping first ;-)

> I can revert it if you don't want me to take it for 6.3-final
> through my driver core tree.

I'll let spi-nor maintainers decide what they prefer.

Thanks,
Miquèl