[V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[Arvind Yadav]

Here, If devm_ioremap will fail. It will return NULL.
Kernel can run into a NULL-pointer dereference.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
---
 drivers/mtd/devices/docg3.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index b833e6c..ffe3db0 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -2083,9 +2083,14 @@ static int __init docg3_probe(struct platform_device *pdev)
 		dev_err(dev, "No I/O memory resource defined\n");
 		return ret;
 	}
-	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
 
 	ret = -ENOMEM;
+	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
+	if (!base) {
+		dev_err(dev, "failed to map I/O memory\n");
+		return ret;
+	}
+
 	cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,
 			       GFP_KERNEL);
 	if (!cascade)
-- 
2.7.4

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[Marek Vasut]

On 12/12/2016 04:00 AM, Arvind Yadav wrote:
> Here, If devm_ioremap will fail. It will return NULL.
> Kernel can run into a NULL-pointer dereference.
> 
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
> ---
>  drivers/mtd/devices/docg3.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
> index b833e6c..ffe3db0 100644
> --- a/drivers/mtd/devices/docg3.c
> +++ b/drivers/mtd/devices/docg3.c
> @@ -2083,9 +2083,14 @@ static int __init docg3_probe(struct platform_device *pdev)
>  		dev_err(dev, "No I/O memory resource defined\n");
>  		return ret;
>  	}
> -	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
>  
>  	ret = -ENOMEM;
> +	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
> +	if (!base) {
> +		dev_err(dev, "failed to map I/O memory\n");
> +		return ret;

Um, return -ENOMEM right away ?

Otherwise,
Acked-by: Marek Vasut <marek.vasut@gmail.com>

> +	}
> +
>  	cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,
>  			       GFP_KERNEL);
>  	if (!cascade)
> 


-- 
Best regards,
Marek Vasut

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[Boris Brezillon]

On Mon, 12 Dec 2016 08:30:04 +0530
Arvind Yadav <arvind.yadav.cs@gmail.com> wrote:

> Here, If devm_ioremap will fail. It will return NULL.
> Kernel can run into a NULL-pointer dereference.
> 
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
> ---
>  drivers/mtd/devices/docg3.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
> index b833e6c..ffe3db0 100644
> --- a/drivers/mtd/devices/docg3.c
> +++ b/drivers/mtd/devices/docg3.c
> @@ -2083,9 +2083,14 @@ static int __init docg3_probe(struct platform_device *pdev)
>  		dev_err(dev, "No I/O memory resource defined\n");
>  		return ret;
>  	}
> -	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
>  
>  	ret = -ENOMEM;
> +	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
> +	if (!base) {
> +		dev_err(dev, "failed to map I/O memory\n");
> +		return ret;
> +	}
> +
>  	cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,
>  			       GFP_KERNEL);
>  	if (!cascade)

How about going even further and doing the following?
This way you can drop the test on rres (it's done for you in
devm_ioremap_resource()), and you can directly return the error
returned by devm_ioremap_resource().

--->8---
diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index b833e6cc684c..c59b91734344 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -2077,13 +2077,10 @@ static int __init docg3_probe(struct
platform_device *pdev) int ret, floor;
        struct docg3_cascade *cascade;
 
-       ret = -ENXIO;
        ress = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-       if (!ress) {
-               dev_err(dev, "No I/O memory resource defined\n");
-               return ret;
-       }
-       base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
+       base = devm_ioremap_resource(dev, ress);
+       if (IS_ERR(base))
+               return PTR_ERR(base);
 
        ret = -ENOMEM;
        cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[arvind Yadav]

There is problem, if you will use devm_ioremap_resource instead of 
devm_ioremap,
than devm_ioremap_resource will call request_mem_region().
request_mem_region() allows to tell the kernel that this driver is going 
to use
this range of I/O addresses, which will prevent other drivers to make an
overlapping call to request_mem_region If other driver want to use same 
address
space to access then it will not allow. Means we can not share same 
address space
between two driver.

Thanks
-Arvind

On Monday 12 December 2016 02:12 PM, Boris Brezillon wrote:
> On Mon, 12 Dec 2016 08:30:04 +0530
> Arvind Yadav <arvind.yadav.cs@gmail.com> wrote:
>
>> Here, If devm_ioremap will fail. It will return NULL.
>> Kernel can run into a NULL-pointer dereference.
>>
>> Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
>> ---
>>   drivers/mtd/devices/docg3.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
>> index b833e6c..ffe3db0 100644
>> --- a/drivers/mtd/devices/docg3.c
>> +++ b/drivers/mtd/devices/docg3.c
>> @@ -2083,9 +2083,14 @@ static int __init docg3_probe(struct platform_device *pdev)
>>   		dev_err(dev, "No I/O memory resource defined\n");
>>   		return ret;
>>   	}
>> -	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
>>   
>>   	ret = -ENOMEM;
>> +	base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
>> +	if (!base) {
>> +		dev_err(dev, "failed to map I/O memory\n");
>> +		return ret;
>> +	}
>> +
>>   	cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,
>>   			       GFP_KERNEL);
>>   	if (!cascade)
> How about going even further and doing the following?
> This way you can drop the test on rres (it's done for you in
> devm_ioremap_resource()), and you can directly return the error
> returned by devm_ioremap_resource().
>
> --->8---
> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
> index b833e6cc684c..c59b91734344 100644
> --- a/drivers/mtd/devices/docg3.c
> +++ b/drivers/mtd/devices/docg3.c
> @@ -2077,13 +2077,10 @@ static int __init docg3_probe(struct
> platform_device *pdev) int ret, floor;
>          struct docg3_cascade *cascade;
>   
> -       ret = -ENXIO;
>          ress = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -       if (!ress) {
> -               dev_err(dev, "No I/O memory resource defined\n");
> -               return ret;
> -       }
> -       base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE);
> +       base = devm_ioremap_resource(dev, ress);
> +       if (IS_ERR(base))
> +               return PTR_ERR(base);
>   
>          ret = -ENOMEM;
>          cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[Robert Jarzmik]

arvind Yadav <arvind.yadav.cs@gmail.com> writes:

> There is problem, if you will use devm_ioremap_resource instead of devm_ioremap,
> than devm_ioremap_resource will call request_mem_region().
> request_mem_region() allows to tell the kernel that this driver is going to use
> this range of I/O addresses, which will prevent other drivers to make an
> overlapping call to request_mem_region If other driver want to use same address
> space to access then it will not allow. Means we can not share same address
> space
> between two driver.

Hi,

You're right Arvind, and still, it's worth noticing that the docg3 access
semantics imply a "reserved" resource path (see how doc_register_readb() does a
write and how this cannot be shared with another driver).

Therefore I'll be willing to ack a mix of your both patches, the
devm_ioremap_resource() from Boris and the error message from your patch.

Cheers.

--
Robert

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[Boris Brezillon]

On Mon, 12 Dec 2016 17:32:58 +0100
Robert Jarzmik <robert.jarzmik@free.fr> wrote:

> arvind Yadav <arvind.yadav.cs@gmail.com> writes:
> 
> > There is problem, if you will use devm_ioremap_resource instead of devm_ioremap,
> > than devm_ioremap_resource will call request_mem_region().
> > request_mem_region() allows to tell the kernel that this driver is going to use
> > this range of I/O addresses, which will prevent other drivers to make an
> > overlapping call to request_mem_region If other driver want to use same address
> > space to access then it will not allow. Means we can not share same address
> > space
> > between two driver.  
> 
> Hi,
> 
> You're right Arvind, and still, it's worth noticing that the docg3 access
> semantics imply a "reserved" resource path (see how doc_register_readb() does a
> write and how this cannot be shared with another driver).
> 
> Therefore I'll be willing to ack a mix of your both patches, the
> devm_ioremap_resource() from Boris and the error message from your patch.

devm_ioremap_resource() already prints different error messages
depending on the error type [1], no need to duplicate it.

[1]http://lxr.free-electrons.com/source/lib/devres.c#L134

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[Boris Brezillon]

Hi Arvind,

On Mon, 12 Dec 2016 21:33:05 +0530
arvind Yadav <arvind.yadav.cs@gmail.com> wrote:

> There is problem, if you will use devm_ioremap_resource instead of 
> devm_ioremap,
> than devm_ioremap_resource will call request_mem_region().
> request_mem_region() allows to tell the kernel that this driver is going 
> to use
> this range of I/O addresses, which will prevent other drivers to make an
> overlapping call to request_mem_region If other driver want to use same 
> address
> space to access then it will not allow. Means we can not share same 
> address space
> between two driver.

The question is, is it required here? In general, allowing 2 different
drivers from touching the same iomem region is a bad idea, so, if
there's a reason to allow that here, I'd like to know more about it.

Thanks,

Boris

Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap.

[arvind Yadav]

Hi Boris,

Yes, It's possible that two driver can use same iomem region.
For example you can check
commit id - : 33cf75656923ff11d67a937a4f8e9344f58cea77

Here, It's not required.

Thanks
-Arvind

On Monday 12 December 2016 10:34 PM, Boris Brezillon wrote:
> Hi Arvind,
>
> On Mon, 12 Dec 2016 21:33:05 +0530
> arvind Yadav <arvind.yadav.cs@gmail.com> wrote:
>
>> There is problem, if you will use devm_ioremap_resource instead of
>> devm_ioremap,
>> than devm_ioremap_resource will call request_mem_region().
>> request_mem_region() allows to tell the kernel that this driver is going
>> to use
>> this range of I/O addresses, which will prevent other drivers to make an
>> overlapping call to request_mem_region If other driver want to use same
>> address
>> space to access then it will not allow. Means we can not share same
>> address space
>> between two driver.
> The question is, is it required here? In general, allowing 2 different
> drivers from touching the same iomem region is a bad idea, so, if
> there's a reason to allow that here, I'd like to know more about it.
>
> Thanks,
>
> Boris