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SubjectRe: [PATCH] w1: Misuse of get_user()/put_user() reported by sparse
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Le 26/11/2021 à 17:00, Greg Kroah-Hartman a écrit :
> On Fri, Nov 19, 2021 at 10:15:09AM +0100, Christophe Leroy wrote:
>> sparse warnings: (new ones prefixed by >>)
>>>> drivers/w1/slaves/w1_ds28e04.c:342:13: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected char [noderef] __user *_pu_addr @@ got char *buf @@
>> drivers/w1/slaves/w1_ds28e04.c:342:13: sparse: expected char [noderef] __user *_pu_addr
>> drivers/w1/slaves/w1_ds28e04.c:342:13: sparse: got char *buf
>>>> drivers/w1/slaves/w1_ds28e04.c:356:13: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected char const [noderef] __user *_gu_addr @@ got char const *buf @@
>> drivers/w1/slaves/w1_ds28e04.c:356:13: sparse: expected char const [noderef] __user *_gu_addr
>> drivers/w1/slaves/w1_ds28e04.c:356:13: sparse: got char const *buf
>>
>> The buffer buf is a failsafe buffer in kernel space, it's not user
>> memory hence doesn't deserve the use of get_user() or put_user().
>>
>> Access 'buf' content directly.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Link: https://lore.kernel.org/lkml/202111190526.K5vb7NWC-lkp@intel.com/T/
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>> drivers/w1/slaves/w1_ds28e04.c | 10 ++--------
>> 1 file changed, 2 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/w1/slaves/w1_ds28e04.c b/drivers/w1/slaves/w1_ds28e04.c
>> index e4f336111edc..d75bb16fb7a1 100644
>> --- a/drivers/w1/slaves/w1_ds28e04.c
>> +++ b/drivers/w1/slaves/w1_ds28e04.c
>> @@ -339,10 +339,7 @@ static BIN_ATTR_RW(pio, 1);
>> static ssize_t crccheck_show(struct device *dev, struct device_attribute *attr,
>> char *buf)
>> {
>> - if (put_user(w1_enable_crccheck + 0x30, buf))
>> - return -EFAULT;
>> -
>> - return sizeof(w1_enable_crccheck);
>> + return sprintf(buf, "%d", w1_enable_crccheck);
>
> This should be sysfs_emit(), right?

Ok

>
>> }
>>
>> static ssize_t crccheck_store(struct device *dev, struct device_attribute *attr,
>> @@ -353,11 +350,8 @@ static ssize_t crccheck_store(struct device *dev, struct device_attribute *attr,
>> if (count != 1 || !buf)
>> return -EINVAL;
>>
>> - if (get_user(val, buf))
>> - return -EFAULT;
>> -
>> /* convert to decimal */
>> - val = val - 0x30;
>> + val = *buf - 0x30;
>
> Why not use a proper function that can parse a string and turn it into a
> number?

I wanted to keep the change minimal. But I can also replace it with some
scanf.

But don't we have any generic function to read and store a bool after all ?

Thanks
Christophe

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