linux-kernel - Re: [PATCH] kernel/irq/irqdomain.c: fix memory leak with using debugfs

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Message-ID: <Y9yj9R1ZzD6GIhdf@kroah.com>
Date:   Fri, 3 Feb 2023 07:04:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] kernel/irq/irqdomain.c: fix memory leak with using
 debugfs_lookup()

On Thu, Feb 02, 2023 at 04:56:50PM +0000, Marc Zyngier wrote:
> On Thu, 02 Feb 2023 16:51:50 +0000,
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> > 
> > On Thu, Feb 02, 2023 at 04:48:30PM +0000, Marc Zyngier wrote:
> > > On Thu, 02 Feb 2023 15:15:54 +0000,
> > > Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> > > > 
> > > > When calling debugfs_lookup() the result must have dput() called on it,
> > > > otherwise the memory will leak over time.  To make things simpler, just
> > > > call debugfs_lookup_and_remove() instead which handles all of the logic
> > > > at once.
> > > > 
> > > > Cc: Marc Zyngier <maz@...nel.org>
> > > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > > Cc: linux-kernel@...r.kernel.org
> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > > ---
> > > >  kernel/irq/irqdomain.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> > > > index 8fe1da9614ee..e2096b51c004 100644
> > > > --- a/kernel/irq/irqdomain.c
> > > > +++ b/kernel/irq/irqdomain.c
> > > > @@ -1915,7 +1915,7 @@ static void debugfs_add_domain_dir(struct irq_domain *d)
> > > >  
> > > >  static void debugfs_remove_domain_dir(struct irq_domain *d)
> > > >  {
> > > > -	debugfs_remove(debugfs_lookup(d->name, domain_dir));
> > > > +	debugfs_lookup_and_remove(d->name, domain_dir);
> > > >  }
> > > >  
> > > >  void __init irq_domain_debugfs_init(struct dentry *root)
> > > 
> > > Reviewed-by: Marc Zyngier <maz@...nel.org>
> > > 
> > > Maybe add a Cc stable to get this in 6.1?
> > 
> > Sure, I can, but how often are irq domains removed from the system under
> > a normal operation?
> 
> As many time as you want if you're doing virtualisation and have the
> right sort of HW (anything GICv4.x, for example, which will create
> per-VM irqdomains).

Ok, I'll queue this up now and get it to Linus for 6.2-final.

thanks,

greg k-h