linux-kernel - Re: [PATCH] irqchip/atmel-aic: Fix potential deadlock in ->xlate()

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Date:   Tue, 13 Sep 2016 15:00:54 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Nicolas Ferre <nicolas.ferre@...el.com>,
        Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-kernel@...r.kernel.org, stable@...nel.vger.org
Subject: Re: [PATCH] irqchip/atmel-aic: Fix potential deadlock in ->xlate()

On Tue, 13 Sep 2016 14:55:20 +0200 (CEST)
Thomas Gleixner <tglx@...utronix.de> wrote:

> On Tue, 13 Sep 2016, Boris Brezillon wrote:
> 
> > aic5_irq_domain_xlate() and aic_irq_domain_xlate() take the generic chip
> > lock without disabling interrupts, which can lead to a deadlock if an
> > interrupt occurs while the lock is held in one of these functions.
> > 
> > Replace irq_gc_{lock,unlock}() calls by
> > raw_spin_{lock_irqsave,unlock_irqrestore}() ones to prevent this bug from
> > happening.
> > 
> > Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > Fixes: b1479ebb7720 ("irqchip: atmel-aic: Add atmel AIC/AIC5 drivers")
> > Cc: <stable@...nel.vger.org>
> > ---
> >  drivers/irqchip/irq-atmel-aic.c  | 5 +++--
> >  drivers/irqchip/irq-atmel-aic5.c | 5 +++--
> >  2 files changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/irqchip/irq-atmel-aic.c b/drivers/irqchip/irq-atmel-aic.c
> > index 112e17c2768b..447a8b0f1395 100644
> > --- a/drivers/irqchip/irq-atmel-aic.c
> > +++ b/drivers/irqchip/irq-atmel-aic.c
> > @@ -176,6 +176,7 @@ static int aic_irq_domain_xlate(struct irq_domain *d,
> >  {
> >  	struct irq_domain_chip_generic *dgc = d->gc;
> >  	struct irq_chip_generic *gc;
> > +	unsigned long flags;
> >  	unsigned smr;
> >  	int idx;
> >  	int ret;
> > @@ -194,11 +195,11 @@ static int aic_irq_domain_xlate(struct irq_domain *d,
> >  
> >  	gc = dgc->gc[idx];
> >  
> > -	irq_gc_lock(gc);
> > +	raw_spin_lock_irqsave(&gc->lock, flags);  
> 
> Please provide a primitive, i.e. irq_gc_lock_irqsave(), for it.

Sure, but that means flagging this patch for stable as well. Are you
okay with that?

> 
> Thanks,
> 
> 	tglx