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Subject: Re: [PATCH] nvmem: core: add sanity check in nvmem_device_read()
To:     Sakari Ailus <sakari.ailus@linux.intel.com>,
        Bingbu Cao <bingbu.cao@intel.com>
Cc:     linux-kernel@vger.kernel.org, bingbu.cao@linux.intel.com
References: <1596532436-19073-1-git-send-email-bingbu.cao@intel.com>
 <20200804095815.GF13316@paasikivi.fi.intel.com>
From:   Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Message-ID: <0e8d60cf-7f8b-c6ab-4184-b869c16b603e@linaro.org>
Date:   Tue, 4 Aug 2020 11:03:26 +0100
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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@intel.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

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