linux-kernel - Re: [PATCH] irqchip/tango: Add NULL check after memory operation

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Message-ID: <yw1xh87efnzd.fsf@mansr.com>
Date:   Mon, 22 Jul 2019 09:54:46 +0100
From:   Måns Rullgård <mans@...sr.com>
To:     Hariprasad Kelam <hariprasad.kelam@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] irqchip/tango: Add NULL check after memory operation

Hariprasad Kelam <hariprasad.kelam@...il.com> writes:

> Add NULL check after kzalloc operation.
>
> Fix below issue reported by coccicheck
> ./drivers/irqchip/irq-tango.c:189:1-5: alloc with no test, possible
> model on line 193
>
> Signed-off-by: Hariprasad Kelam <hariprasad.kelam@...il.com>
> ---
>  drivers/irqchip/irq-tango.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/irqchip/irq-tango.c b/drivers/irqchip/irq-tango.c
> index 34290f0..761b9fa 100644
> --- a/drivers/irqchip/irq-tango.c
> +++ b/drivers/irqchip/irq-tango.c
> @@ -187,6 +187,8 @@ static int __init tangox_irq_init(void __iomem *base, struct resource *baseres,
>  		panic("%pOFn: failed to get address", node);
>
>  	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
> +	if (!chip)
> +		return -ENOMEM;
>  	chip->ctl = res.start - baseres->start;
>  	chip->base = base;
>
> -- 

Nothing checks the return value of that function, so bad things will
still happen, only more confusing to debug.  If you really want to
"fix" this, you should either:

- Simply panic() like the other error cases.  If anything here fails,
  the system will not work anyway.

- Replace the panic() calls with error returns and check the return
  value in tangox_of_irq_init().  The system will still end up unusable.

-- 
Måns Rullgård