linux-kernel - Re: [PATCH] ARM: OMAP: Fix use of possibly uninitialized irq variable

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Date:   Thu, 1 Apr 2021 09:45:52 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Maciej Falkowski <maciej.falkowski9@...il.com>
Cc:     khilman@...nel.org, aaro.koskinen@....fi, tony@...mide.com,
        linux@...linux.org.uk, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] ARM: OMAP: Fix use of possibly uninitialized irq variable

On Thu, Apr 01, 2021 at 06:11:27PM +0200, Maciej Falkowski wrote:
> The current control flow of IRQ number assignment to `irq` variable
> allows a request of IRQ of unspecified value,
> generating a warning under Clang compilation with omap1_defconfig on linux-next:
> 
> arch/arm/mach-omap1/pm.c:656:11: warning: variable 'irq' is used uninitialized whenever
> 'if' condition is false [-Wsometimes-uninitialized]
>         else if (cpu_is_omap16xx())
>                  ^~~~~~~~~~~~~~~~~
> ./arch/arm/mach-omap1/include/mach/soc.h:123:30: note: expanded from macro 'cpu_is_omap16xx'
>                                         ^~~~~~~~~~~~~
> arch/arm/mach-omap1/pm.c:658:18: note: uninitialized use occurs here
>         if (request_irq(irq, omap_wakeup_interrupt, 0, "peripheral wakeup",
>                         ^~~
> arch/arm/mach-omap1/pm.c:656:7: note: remove the 'if' if its condition is always true
>         else if (cpu_is_omap16xx())
>              ^~~~~~~~~~~~~~~~~~~~~~
> arch/arm/mach-omap1/pm.c:611:9: note: initialize the variable 'irq' to silence this warning
>         int irq;
>                ^
>                 = 0
> 1 warning generated.
> 
> The patch provides a default value to the `irq` variable
> along with a validity check.
> 

Might be worth a fixes tag:

Fixes: b75ca5217743 ("ARM: OMAP: replace setup_irq() by request_irq()")

> Signed-off-by: Maciej Falkowski <maciej.falkowski9@...il.com>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1324

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  arch/arm/mach-omap1/pm.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-omap1/pm.c b/arch/arm/mach-omap1/pm.c
> index 2c1e2b32b9b3..a745d64d4699 100644
> --- a/arch/arm/mach-omap1/pm.c
> +++ b/arch/arm/mach-omap1/pm.c
> @@ -655,9 +655,13 @@ static int __init omap_pm_init(void)
>  		irq = INT_7XX_WAKE_UP_REQ;
>  	else if (cpu_is_omap16xx())
>  		irq = INT_1610_WAKE_UP_REQ;
> -	if (request_irq(irq, omap_wakeup_interrupt, 0, "peripheral wakeup",
> -			NULL))
> -		pr_err("Failed to request irq %d (peripheral wakeup)\n", irq);
> +	else
> +		irq = -1;
> +
> +	if (irq >= 0) {
> +		if (request_irq(irq, omap_wakeup_interrupt, 0, "peripheral wakeup", NULL))
> +			pr_err("Failed to request irq %d (peripheral wakeup)\n", irq);
> +	}
>  
>  	/* Program new power ramp-up time
>  	 * (0 for most boards since we don't lower voltage when in deep sleep)
> -- 
> 2.26.3
>