Messages in this thread | | | Date | Wed, 8 Feb 2023 15:50:19 +0100 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH v2] mtd: spi-nor: fix memory leak when using debugfs_lookup() |
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On Wed, Feb 08, 2023 at 03:24:31PM +0100, Michael Walle wrote: > Am 2023-02-08 15:12, schrieb Greg Kroah-Hartman: > > On Wed, Feb 08, 2023 at 02:36:23PM +0100, Michael Walle wrote: > > > Am 2023-02-08 13:57, schrieb Greg Kroah-Hartman: > > > > When calling debugfs_lookup() the result must have dput() called on it, > > > > otherwise the memory will leak over time. > > > > > > > > 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> > > > > --- > > > > v2: fix up to work when module is removed and added, making the fix > > > > much simpler. > > > > > > > > drivers/mtd/spi-nor/debugfs.c | 1 + > > > > 1 file changed, 1 insertion(+) > > > > > > > > diff --git a/drivers/mtd/spi-nor/debugfs.c > > > > b/drivers/mtd/spi-nor/debugfs.c > > > > index ff895f6758ea..af41fbc09a97 100644 > > > > --- a/drivers/mtd/spi-nor/debugfs.c > > > > +++ b/drivers/mtd/spi-nor/debugfs.c > > > > @@ -242,6 +242,7 @@ void spi_nor_debugfs_register(struct spi_nor *nor) > > > > > > > > d = debugfs_create_dir(dev_name(nor->dev), rootdir); > > > > nor->debugfs_root = d; > > > > + dput(rootdir); > > > > > > rootdir might either be the return value of debugfs_lookup() or > > > debugfs_create_dir(). dput() is probably wrong for the latter, > > > right? Also there is an early return, where the dput() is missing, > > > too. > > > > {sigh} > > > > Yeah, this is all wrong, sorry. Let me fix this up again, properly. > > And to do it properly, let's have the module remove the directory if it > > is unloaded, like a good module should :) > > There were some complications. IIRC you'd need to do reference counting, > to determine whether you are the last user of the rootdir. Other subsys > create an empty rootdir in their .init(). But that was hard to do in MTD. > Again memory is hazy.. Therefore, I resorted to create it on the fly if > there isn't already one. > > Maybe you got some better/simpler idea :)
Yup, just do it normally like other drivers, I'll send a v3 now.
thanks,
greg k-h
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