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SubjectRe: [PATCH] mtd: spi-nor: fix memory leak when using debugfs_lookup()
On Fri, Sep 02, 2022 at 04:01:36PM +0200, Michael Walle wrote:
> Hi,
>
> Am 2022-09-02 15:37, schrieb Greg Kroah-Hartman:
> > When calling debugfs_lookup() the result must have dput() called on it,
> > otherwise the memory will leak over time. Fix this up to be much
> > simpler logic and only create the root debugfs directory once when the
> > driver is first accessed. That resolves the memory leak and makes
> > things more obvious as to what the intent is.
> >
> > Cc: Tudor Ambarus <tudor.ambarus@microchip.com>
> > Cc: Pratyush Yadav <pratyush@kernel.org>
> > Cc: Michael Walle <michael@walle.cc>
> > Cc: Miquel Raynal <miquel.raynal@bootlin.com>
> > Cc: Richard Weinberger <richard@nod.at>
> > Cc: Vignesh Raghavendra <vigneshr@ti.com>
> > Cc: linux-mtd@lists.infradead.org
> > Cc: stable <stable@kernel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> > drivers/mtd/spi-nor/debugfs.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mtd/spi-nor/debugfs.c
> > b/drivers/mtd/spi-nor/debugfs.c
> > index df76cb5de3f9..3aab595e82d1 100644
> > --- a/drivers/mtd/spi-nor/debugfs.c
> > +++ b/drivers/mtd/spi-nor/debugfs.c
> > @@ -228,11 +228,11 @@ static void spi_nor_debugfs_unregister(void *data)
> >
> > void spi_nor_debugfs_register(struct spi_nor *nor)
> > {
> > - struct dentry *rootdir, *d;
> > + static struct dentry *rootdir;
> > + struct dentry *d;
> > int ret;
> >
> > /* Create rootdir once. Will never be deleted again. */
> > - rootdir = debugfs_lookup(SPI_NOR_DEBUGFS_ROOT, NULL);
>
> IIRC I had that one and it didn't work with spi-nor as a module.
> Wouldn't it try to create the root dir twice if you remove the module
> and load it again?

Yes it would, that is a use-model I did not consider at all, thanks.
I'll rework this.

greg k-h

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