[PATCH] gpio: davinci: Fix potential buffer overflow

[PATCH] gpio: davinci: Fix potential buffer overflow

[Aleksandr Mishin]

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@t-argos.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;
+	}
 	for (bank = 0; bank < nbank; bank++)
 		chips->regs[bank] = gpio_base + offset_array[bank];
 
-- 
2.30.2

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

[Dan Carpenter]

On Thu, Mar 28, 2024 at 12:10:21PM +0300, Aleksandr Mishin wrote:
> 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.
                                        ^^

Where does this 63 come from?  SVACE is a static analysis tool.  I would
have thought a static checker would say that 'bank' goes up to
UINT_MAX / 32.

This stuff comes from device tree though, so it looks fine to me.

Documentation/devicetree/bindings/gpio/gpio-davinci.yaml:      ti,ngpio = <144>;
Documentation/devicetree/bindings/gpio/gpio-davinci.yaml:      ti,ngpio = <32>;
Documentation/devicetree/bindings/gpio/gpio-davinci.yaml:      ti,ngpio = <56>;
arch/arm/boot/dts/ti/davinci/da850.dtsi:                        ti,ngpio = <144>;

So it's fine.

I'm not the maintainer of this file so I don't know if adding a sanity
check makes sense but if we wanted to do that we'd have to add it to
davinci_gpio_get_pdata().  Otherwise it would have already had a buffer
overflow earlier in the probe function when we do:

drivers/gpio/gpio-davinci.c
   223          if (pdata->gpio_unbanked)
   224                  nirq = pdata->gpio_unbanked;
   225          else
   226                  nirq = DIV_ROUND_UP(ngpio, 16);
   227  
   228          chips = devm_kzalloc(dev, sizeof(*chips), GFP_KERNEL);
   229          if (!chips)
   230                  return -ENOMEM;
   231  
   232          gpio_base = devm_platform_ioremap_resource(pdev, 0);
   233          if (IS_ERR(gpio_base))
   234                  return PTR_ERR(gpio_base);
   235  
   236          for (i = 0; i < nirq; i++) {
   237                  chips->irqs[i] = platform_get_irq(pdev, i);
                                   ^^^

   238                  if (chips->irqs[i] < 0)
   239                          return chips->irqs[i];
   240          }

regards,
dan carpenter

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

[Alexander Lobakin]

From: Aleksandr Mishin <amishin@t-argos.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@t-argos.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

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

[Aleksandr Mishin]

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

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

[Alexander Lobakin]

From: Aleksandr Mishin <amishin@t-argos.ru>
Date: Thu, 28 Mar 2024 19:23:56 +0300

> 
> 
> 28.03.2024 18:27, Alexander Lobakin пишет:
>> From: Aleksandr Mishin <amishin@t-argos.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@t-argos.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/).
> 

But no real hardware / device tree which declares such huge number of
GPIOs, right?

CONFIG_ARCH_NR_GPIO is architecture-specific. Davinci is a platform, not
an architecture. If no Davinci board can have a number that would
overflow, the fix doesn't make sense.

Thanks,
Olek

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

[Dan Carpenter]

On Thu, Mar 28, 2024 at 04:27:24PM +0100, Alexander Lobakin wrote:
> > 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.

This patch isn't correct, but we merge a few static checker fixes every
day.

regards,
dan carpenter