linux-kernel - Re: [PATCH net] net: mvpp2: debugfs: fix problem with previous memory leak fix

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Date:   Thu, 22 Sep 2022 17:05:42 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marcin Wojtas <mw@...ihalf.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, stable <stable@...nel.org>
Subject: Re: [PATCH net] net: mvpp2: debugfs: fix problem with previous
 memory leak fix

On Wed, Sep 21, 2022 at 01:44:44PM +0200, Greg Kroah-Hartman wrote:
> In commit fe2c9c61f668 ("net: mvpp2: debugfs: fix memory leak when using
> debugfs_lookup()"), if the module is unloaded, the directory will still
> be present if the module is loaded again and creating the directory will
> fail, causing the creation of additional child debugfs entries for the
> individual devices to fail.
> 
> As this module never cleaned up the root directory it created, even when
> loaded, and unloading/loading a module is not a normal operation, none
> of would normally happen.
> 
> To clean all of this up, use a tiny reference counted structure to hold
> the root debugfs directory for the driver, and then clean it up when the
> last user of it is removed from the system.  This should resolve the
> previously reported problems, and the original memory leak that
> fe2c9c61f668 ("net: mvpp2: debugfs: fix memory leak when using
> debugfs_lookup()") was attempting to fix.

For the record... I have a better fix for this, but I haven't been able
to get it into a state suitable for submission yet.

http://www.home.armlinux.org.uk/~rmk/misc/mvpp2-debugfs.diff

Not yet against the net tree. Might have time tomorrow to do that, not
sure at the moment. Medical stuff is getting in the way. :(

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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