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

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Message-ID: <4b306a43-7b8f-e4c4-95f8-bb0cd52f4336@gmail.com>
Date:   Tue, 17 Jan 2017 15:40:02 +0530
From:   Arvind Yadav <arvind.yadav.cs@...il.com>
To:     Marc Zyngier <marc.zyngier@....com>, tglx@...utronix.de,
        jason@...edaemon.net, matt.redfearn@...tec.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] irqchip: irq-mips-gic:- Handle return NULL error from
 ioremap_nocache

Hi Matt,

Please Acknowledge this.

Regards
Arvind Yadav

On Monday 09 January 2017 02:30 PM, Marc Zyngier wrote:
> 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.