linux-kernel - Re: [PATCH] gpio: davinci: Fix potential buffer overflow

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Date: Thu, 28 Mar 2024 19:23:56 +0300
From: Aleksandr Mishin <amishin@...rgos.ru>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
CC: Keerthy <j-keerthy@...com>, Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>, "Andrew F. Davis" <afd@...com>,
	<linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<"<lvc-project"@linuxtesting.org>
Subject: Re: [PATCH] gpio: davinci: Fix potential buffer overflow



28.03.2024 18:27, Alexander Lobakin пишет:
> From: Aleksandr Mishin <amishin@...rgos.ru>
> 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@...rgos.ru>
>> ---
>>   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
> 

I can only see the code at this time. And I see the following:
1. In some configurations CONFIG_ARCH_NR_GPIO value is 2048. So nbank 
value can be 64.
2. Previously, a patch was proposed that removes restrictions on the 
number of GPIOs 
(https://lore.kernel.org/all/cb540a9d73cad36d288664f8b275c6308a4a3168.1662116601.git.christophe.leroy@csgroup.eu/).

-- 
Kind regards
Aleksandr