linux-kernel - Re: [PATCH] nvmem: core: add sanity check in nvmem_device

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Date:   Tue, 4 Aug 2020 18:44:27 +0800
From:   Bingbu Cao <bingbu.cao@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Bingbu Cao <bingbu.cao@...el.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvmem: core: add sanity check in nvmem_device_read()


On 8/4/20 6:03 PM, Srinivas Kandagatla wrote:
> 
> 
> On 04/08/2020 10:58, Sakari Ailus wrote:
>> Hi Bingbu,
>>
>> Thank you for the patch.
>>
>> On Tue, Aug 04, 2020 at 05:13:56PM +0800, Bingbu Cao wrote:
>>> nvmem_device_read() could be called directly once nvmem device
>>> registered, the sanity check should be done before call
>>> nvmem_reg_read() as cell and sysfs read did now.
>>>
>>> Signed-off-by: Bingbu Cao <bingbu.cao@...el.com>
>>> ---
>>>   drivers/nvmem/core.c | 7 +++++++
>>>   1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
>>> index 927eb5f6003f..c9a77993f008 100644
>>> --- a/drivers/nvmem/core.c
>>> +++ b/drivers/nvmem/core.c
>>> @@ -1491,6 +1491,13 @@ int nvmem_device_read(struct nvmem_device *nvmem,
>>>       if (!nvmem)
>>>           return -EINVAL;
>>>   +    if (offset >= nvmem->size || bytes < nvmem->word_size)
>>> +        return 0;
>>> +
>>> +    if (bytes + offset > nvmem->size)
>>> +        bytes = nvmem->size - offset;
>>
>> The check is relevant for nvmem_device_write(), too.
>>
>> There are also other ways to access nvmem devices such as nvmem_cell_read
>> and others alike. Should they be considered as well?
> 
> We should probably move these sanity checks to a common place like
> nvmem_reg_read() and nvmem_reg_write(), so the callers need not duplicate the same!
> 
Srini and Sakari, thanks for your review.

Is it OK just return INVAL with simple check like below?

if (bytes + offset > nvmem->size ||
    bytes != round_down(bytes, nvmem->word_size))
        return -EINVAL;


> --srini
> 
>>
>>> +
>>> +    bytes = round_down(bytes, nvmem->word_size);
>>>       rc = nvmem_reg_read(nvmem, offset, buf, bytes);
>>>         if (rc)
>>

-- 
Best regards,
Bingbu Cao