linux-kernel - Re: [PATCH] nvmem: core: make default user binary file root-access only

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Date:	Wed, 07 Oct 2015 18:01:03 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	maxime.ripard@...e-electrons.com, linux-kernel@...r.kernel.org,
	andrew@...n.ch, wxt@...k-chips.com, stefan.wahren@...e.com,
	pantelis.antoniou@...sulko.com, maitysanchayan@...il.com,
	p.zabel@...gutronix.de, s.hauer@...gutronix.de,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] nvmem: core: make default user binary file root-access
 only



On 07/10/15 17:50, Greg KH wrote:
> On Wed, Oct 07, 2015 at 05:35:14PM +0100, Srinivas Kandagatla wrote:
>> As required by many providers like at24/at25/mxs-ocotp/qfprom, which would
>> want to allow root-only to read/write the nvmem content.
>> So making the defaults to be root-only access which can prevent normal
>> users from reading the nvmem data.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>   drivers/nvmem/core.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
>> index 6fd4e5a..4d2e476 100644
>> --- a/drivers/nvmem/core.c
>> +++ b/drivers/nvmem/core.c
>> @@ -112,7 +112,7 @@ static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
>>   static struct bin_attribute bin_attr_rw_nvmem = {
>>   	.attr	= {
>>   		.name	= "nvmem",
>> -		.mode	= S_IWUSR | S_IRUGO,
>> +		.mode	= S_IWUSR | S_IRUSR,
>>   	},
>>   	.read	= bin_attr_nvmem_read,
>>   	.write	= bin_attr_nvmem_write,
>> @@ -136,7 +136,7 @@ static const struct attribute_group *nvmem_rw_dev_groups[] = {
>>   static struct bin_attribute bin_attr_ro_nvmem = {
>>   	.attr	= {
>>   		.name	= "nvmem",
>> -		.mode	= S_IRUGO,
>> +		.mode	= S_IRUSR,
>>   	},
>>   	.read	= bin_attr_nvmem_read,
>>   };
>
> How about using BIN_ATTR_RO() and friends instead, that way I _know_ you
> got the permissions correct as it's impossible to get them wrong by
> using those macros.
Yes, that sounds good, but there are no macros for just "S_IRUSR" or 
"(S_IWUSR | S_IRUSR)" in ./include/linux/sysfs.h


--srini

>
> thanks,
>
> greg k-h
>
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