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

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Message-ID: <CAPv3WKch2J4tteo68wOt_ETj_eYEKy8EC5sTwDvW6UZ-Gs_sCw@mail.gmail.com>
Date:   Thu, 22 Sep 2022 19:08:16 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "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

Hi,

Thank you both for the patches.


czw., 22 wrz 2022 o 18:05 Russell King (Oracle)
<linux@...linux.org.uk> napisał(a):
>
> 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. :(
>

I'd lean towards this version - it is a bit more compact. I'll try to
test that tomorrow or during the weekend.

Best regards,
Marcin