[PATCH] w1: Misuse of get_user()/put_user() reported by sparse

[Christophe Leroy]

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@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/202111190526.K5vb7NWC-lkp@xxxxxxxxx/T/
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
 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);
 }
 
 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;
 	if (val != 0 && val != 1)
 		return -EINVAL;
 
-- 
2.33.1