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

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Message-ID: <20160913121245.3217e23d@bbrezillon>
Date:   Tue, 13 Sep 2016 12:12:45 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     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 12:10:09 +0200
Boris Brezillon <boris.brezillon@...e-electrons.com> 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.
> 

Forgot to mention that this problem was discovered by kernelci [1].

[1]https://storage.kernelci.org/arm-soc/v4.4-2499-gbb46b50a5130/arm-multi_v7_defconfig+CONFIG_PROVE_LOCKING=y/lab-free-electrons/boot-at91-sama5d3_xplained.html

> 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);
>  	smr = irq_reg_readl(gc, AT91_AIC_SMR(*out_hwirq));
>  	aic_common_set_priority(intspec[2], &smr);
>  	irq_reg_writel(gc, smr, AT91_AIC_SMR(*out_hwirq));
> -	irq_gc_unlock(gc);
> +	raw_spin_unlock_irqrestore(&gc->lock, flags);
>  
>  	return ret;
>  }
> diff --git a/drivers/irqchip/irq-atmel-aic5.c b/drivers/irqchip/irq-atmel-aic5.c
> index 4f0d068e1abe..8c024107fd03 100644
> --- a/drivers/irqchip/irq-atmel-aic5.c
> +++ b/drivers/irqchip/irq-atmel-aic5.c
> @@ -258,6 +258,7 @@ static int aic5_irq_domain_xlate(struct irq_domain *d,
>  				 unsigned int *out_type)
>  {
>  	struct irq_chip_generic *bgc = irq_get_domain_generic_chip(d, 0);
> +	unsigned long flags;
>  	unsigned smr;
>  	int ret;
>  
> @@ -269,12 +270,12 @@ static int aic5_irq_domain_xlate(struct irq_domain *d,
>  	if (ret)
>  		return ret;
>  
> -	irq_gc_lock(bgc);
> +	raw_spin_lock_irqsave(&bgc->lock, flags);
>  	irq_reg_writel(bgc, *out_hwirq, AT91_AIC5_SSR);
>  	smr = irq_reg_readl(bgc, AT91_AIC5_SMR);
>  	aic_common_set_priority(intspec[2], &smr);
>  	irq_reg_writel(bgc, smr, AT91_AIC5_SMR);
> -	irq_gc_unlock(bgc);
> +	raw_spin_unlock_irqrestore(&bgc->lock, flags);
>  
>  	return ret;
>  }