linux-kernel - Re: [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer

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Message-ID: <20190902223650.GJ21922@piout.net>
Date:   Tue, 3 Sep 2019 00:36:50 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Yizhuo <yzhai003@....edu>
Cc:     csong@...ucr.edu, zhiyunq@...ucr.edu,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] clocksource: atmel-st: Variable sr in
 at91rm9200_timer_interrupt() could be uninitialized

On 02/09/2019 15:29:46-0700, Yizhuo wrote:
> Inside function at91rm9200_timer_interrupt(), variable sr could
> be uninitialized if regmap_read() fails. However, sr is used

Could you elaborate on how this could fail?

> to decide the control flow later in the if statement, which is
> potentially unsafe. We could check the return value of
> regmap_read() and print an error here.
> 
> Signed-off-by: Yizhuo <yzhai003@....edu>
> ---
>  drivers/clocksource/timer-atmel-st.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
> index ab0aabfae5f0..061a3f27847e 100644
> --- a/drivers/clocksource/timer-atmel-st.c
> +++ b/drivers/clocksource/timer-atmel-st.c
> @@ -48,8 +48,14 @@ static inline unsigned long read_CRTR(void)
>  static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
>  {
>  	u32 sr;
> +	int ret;
> +
> +	ret = regmap_read(regmap_st, AT91_ST_SR, &sr);
> +	if (ret) {
> +		pr_err("Fail to read AT91_ST_SR.\n");
> +		return ret;
> +	}
>  
> -	regmap_read(regmap_st, AT91_ST_SR, &sr);
>  	sr &= irqmask;
>  
>  	/*
> -- 
> 2.17.1
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com