linux-kernel - Re: [v2] net:ethernet:cavium:octeon:octeon_mgmt: Handle return NULL error from devm

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Message-ID: <0be48286-2656-84b4-4cd8-93bea5fbc6f0@gmail.com>
Date:   Wed, 14 Dec 2016 23:36:21 +0530
From:   arvind Yadav <arvind.yadav.cs@...il.com>
To:     David Daney <ddaney@...iumnetworks.com>, peter.chen@....com,
        fw@...len.de, david.daney@...ium.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [v2] net:ethernet:cavium:octeon:octeon_mgmt: Handle return NULL
 error from devm_ioremap

Yes, I have seen this error. We have a device with very less memory.
Basically it's OMAP2 board. We have to port Android L on this.
It's has 3.10 kernel version. In this device, we were getting Page 
allocation failure.
Vmalloc size was not enough to run all application. So we have decide to
increase vmalloc reserve space. once we increases Vmalloc space.
We start getting ioremap falilure. Kernel is getting NULL-pointer 
dereference error.

Here, It's just check to avoid any kernel crash because of ioremap failure.
We can keep this check to avoid this kind of scenario.

Thanks
-Arvind


On Wednesday 14 December 2016 11:02 PM, David Daney wrote:
> On 12/14/2016 08:25 AM, Arvind Yadav wrote:
>> Here, If devm_ioremap will fail. It will return NULL.
>> Kernel can run into a NULL-pointer dereference.
>> This error check will avoid NULL pointer dereference.
>>
> i
> Have you ever seen this failure in the wild?
>
> How was the patch tested?
>
> Thanks,
> David Daney
>
>
>> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
>> ---
>>  drivers/net/ethernet/cavium/octeon/octeon_mgmt.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/cavium/octeon/octeon_mgmt.c 
>> b/drivers/net/ethernet/cavium/octeon/octeon_mgmt.c
>> index 4ab404f..33c2fec 100644
>> --- a/drivers/net/ethernet/cavium/octeon/octeon_mgmt.c
>> +++ b/drivers/net/ethernet/cavium/octeon/octeon_mgmt.c
>> @@ -1479,6 +1479,12 @@ static int octeon_mgmt_probe(struct 
>> platform_device *pdev)
>>      p->agl = (u64)devm_ioremap(&pdev->dev, p->agl_phys, p->agl_size);
>>      p->agl_prt_ctl = (u64)devm_ioremap(&pdev->dev, p->agl_prt_ctl_phys,
>>                         p->agl_prt_ctl_size);
>> +    if (!p->mix || !p->agl || !p->agl_prt_ctl) {
>> +        dev_err(&pdev->dev, "failed to map I/O memory\n");
>> +        result = -ENOMEM;
>> +        goto err;
>> +    }
>> +
>>      spin_lock_init(&p->lock);
>>
>>      skb_queue_head_init(&p->tx_list);
>>
>