Re: [PATCH] gpio: davinci: Fix potential buffer overflow

[Alexander Lobakin]

From: Aleksandr Mishin <amishin@xxxxxxxxxx>
Date: Thu, 28 Mar 2024 12:10:21 +0300

> In davinci_gpio_probe() accessing an element of array 'chips->regs' of size 5 and
> array 'offset_array' of size 5 can lead to a buffer overflow, since the index
> 'bank' can have an out of range value 63.
> Fix this bug by limiting top index value.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: c809e37a3b5a ("gpio: davinci: Allocate the correct amount of memory for controller")
> Signed-off-by: Aleksandr Mishin <amishin@xxxxxxxxxx>
> ---
>  drivers/gpio/gpio-davinci.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpio/gpio-davinci.c b/drivers/gpio/gpio-davinci.c
> index bb499e362912..b65df1f2b83f 100644
> --- a/drivers/gpio/gpio-davinci.c
> +++ b/drivers/gpio/gpio-davinci.c
> @@ -257,6 +257,9 @@ static int davinci_gpio_probe(struct platform_device *pdev)
>  	spin_lock_init(&chips->lock);
>  
>  	nbank = DIV_ROUND_UP(ngpio, 32);
> +    if (nbank > MAX_REGS_BANKS || nbank > 5) {
> +        nbank = MAX_REGS_BANKS < 5 ? MAX_REGS_BANKS : 5;
> +	}

Static analysis warnings make no sense until you provide a reliable way
to trigger the problem on real systems.

>  	for (bank = 0; bank < nbank; bank++)
>  		chips->regs[bank] = gpio_base + offset_array[bank];
>  

Thanks,
Olek