linux-kernel - Re: [PATCH v2] mtd: spi-nor: fix memory leak when using debugfs

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Date:   Wed, 08 Feb 2023 14:36:23 +0100
From:   Michael Walle <michael@...le.cc>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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, stable <stable@...nel.org>
Subject: Re: [PATCH v2] mtd: spi-nor: fix memory leak when using
 debugfs_lookup()

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@...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
> Cc: stable <stable@...nel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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.

-michael