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

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Date:   Wed, 8 Feb 2023 18:30:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-kernel@...r.kernel.org,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Pratyush Yadav <pratyush@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        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()

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.
> 

Argh, I knew that, for some reason I went back and added that check as I
was thinking this would have been an issue if rootdir was never created.
You are right, it isn't a problem, oh well.

The simplest patches sometimes take the longest time to get right, I'll
stop now :)

thanks so much for the reviews,

greg k-h