linux-kernel - Re: [PATCH v1] irqchip: irq-mips-gic:- Handle return NULL error from ioremap

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Message-ID: <120995f1-6cdb-9736-f6da-b85925f27451@arm.com>
Date:   Mon, 9 Jan 2017 09:00:02 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Arvind Yadav <arvind.yadav.cs@...il.com>, tglx@...utronix.de,
        jason@...edaemon.net
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] irqchip: irq-mips-gic:- Handle return NULL error from
 ioremap_nocache

On 09/01/17 08:08, Arvind Yadav wrote:
> Here, If ioremap_nocache will fail. It will return NULL.
> Kernel can run into a NULL-pointer dereference.
> This error check will avoid NULL pointer dereference.
> 
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
> ---
>  drivers/irqchip/irq-mips-gic.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
> index c01c09e..eeea2e8 100644
> --- a/drivers/irqchip/irq-mips-gic.c
> +++ b/drivers/irqchip/irq-mips-gic.c
> @@ -979,6 +979,8 @@ static void __init __gic_init(unsigned long gic_base_addr,
>  	__gic_base_addr = gic_base_addr;
>  
>  	gic_base = ioremap_nocache(gic_base_addr, gic_addrspace_size);
> +	if (!gic_base)
> +		panic("Failed to map GIC memory");

So you're replacing a panic due to dereferencing a NULL pointer with
another panic -- not much progress here. I appreciate that the message
is a bit more explicit, but is there something slightly less drastic we
could do? Like returning an error code and see if the kernel otherwise
recovers (possibly with reduced functionality)?

>  
>  	gicconfig = gic_read(GIC_REG(SHARED, GIC_SH_CONFIG));
>  	gic_shared_intrs = (gicconfig & GIC_SH_CONFIG_NUMINTRS_MSK) >>
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...