linux-kernel - Re: Patch "net: mvpp2: debugfs: fix memory leak when using debugfs_lookup()" has been added to the 5.10-stable tree

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Date:   Wed, 21 Sep 2022 08:51:48 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     stable-commits@...r.kernel.org, Marcin Wojtas <mw@...ihalf.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: Patch "net: mvpp2: debugfs: fix memory leak when using
 debugfs_lookup()" has been added to the 5.10-stable tree

On Tue, Sep 20, 2022 at 05:46:25PM -0400, Sasha Levin wrote:
> This is a note to let you know that I've just added the patch titled
> 
>     net: mvpp2: debugfs: fix memory leak when using debugfs_lookup()
> 
> to the 5.10-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      net-mvpp2-debugfs-fix-memory-leak-when-using-debugfs.patch
> and it can be found in the queue-5.10 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@...r.kernel.org> know about it.
> 
> 
> 
> commit 24f9e4af2b16c42327cde7198834a5d58aacb2f8
> Author: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Date:   Fri Sep 2 15:41:11 2022 +0200
> 
>     net: mvpp2: debugfs: fix memory leak when using debugfs_lookup()
>     
>     [ Upstream commit fe2c9c61f668cde28dac2b188028c5299cedcc1e ]
>     
>     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: Marcin Wojtas <mw@...ihalf.com>
>     Cc: Russell King <linux@...linux.org.uk>
>     Cc: "David S. Miller" <davem@...emloft.net>
>     Cc: Eric Dumazet <edumazet@...gle.com>
>     Cc: Jakub Kicinski <kuba@...nel.org>
>     Cc: Paolo Abeni <pabeni@...hat.com>
>     Cc: netdev@...r.kernel.org
>     Cc: stable <stable@...nel.org>
>     Fixes: 21da57a23125 ("net: mvpp2: add a debugfs interface for the Header Parser")
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>     Signed-off-by: David S. Miller <davem@...emloft.net>
>     Signed-off-by: Sasha Levin <sashal@...nel.org>
> 
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c
> index 4a3baa7e0142..0eec05d905eb 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c
> @@ -700,10 +700,10 @@ void mvpp2_dbgfs_cleanup(struct mvpp2 *priv)
>  
>  void mvpp2_dbgfs_init(struct mvpp2 *priv, const char *name)
>  {
> -	struct dentry *mvpp2_dir, *mvpp2_root;
> +	static struct dentry *mvpp2_root;
> +	struct dentry *mvpp2_dir;
>  	int ret, i;
>  
> -	mvpp2_root = debugfs_lookup(MVPP2_DRIVER_NAME, NULL);
>  	if (!mvpp2_root)
>  		mvpp2_root = debugfs_create_dir(MVPP2_DRIVER_NAME, NULL);
>  

I dropped this at the request of Russell last time around, and will be
fixing this up in a "better" way later this week, so I will drop this
from the stable queues as well.

thanks,

greg k-h