[PATCH v2] rtlwifi: fix incorrect error codes in rtl_debugfs_set_write_rfreg()

[Wei Chen <harperchen1110@gmail.com>]

If there is a failure during copy_from_user or user-provided data buffer
is invalid, rtl_debugfs_set_write_rfreg should return negative error code
instead of a positive value count.

Fix this bug by returning correct error code. Moreover, the check of buffer
against null is removed since it will be handled by copy_from_user.

Fixes: 610247f46feb ("rtlwifi: Improve debugging by using debugfs")
Signed-off-by: Wei Chen <harperchen1110@gmail.com>
---
Changes in v2:
 - Add fixes commit tag
 - Correct the subject prefix 

 drivers/net/wireless/realtek/rtlwifi/debug.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/debug.c b/drivers/net/wireless/realtek/rtlwifi/debug.c
index 3e7f9b4f1f19..9eb26dfe4ca9 100644
--- a/drivers/net/wireless/realtek/rtlwifi/debug.c
+++ b/drivers/net/wireless/realtek/rtlwifi/debug.c
@@ -375,8 +375,8 @@ static ssize_t rtl_debugfs_set_write_rfreg(struct file *filp,
 
 	tmp_len = (count > sizeof(tmp) - 1 ? sizeof(tmp) - 1 : count);
 
-	if (!buffer || copy_from_user(tmp, buffer, tmp_len))
-		return count;
+	if (copy_from_user(tmp, buffer, tmp_len))
+		return -EFAULT;
 
 	tmp[tmp_len] = '\0';
 
@@ -386,7 +386,7 @@ static ssize_t rtl_debugfs_set_write_rfreg(struct file *filp,
 	if (num != 4) {
 		rtl_dbg(rtlpriv, COMP_ERR, DBG_DMESG,
 			"Format is <path> <addr> <mask> <data>\n");
-		return count;
+		return -EINVAL;
 	}
 
 	rtl_set_rfreg(hw, path, addr, bitmask, data);
-- 
2.25.1