If there is a failure during copy_from_user or user-provided data buffer 
is invalid, rtl_debugfs_set_write_reg 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.

Signed-off-by: Wei Chen <harperchen1110@gmail.com>
---
 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 0b1bc04cb6ad..3e7f9b4f1f19 100644
--- a/drivers/net/wireless/realtek/rtlwifi/debug.c
+++ b/drivers/net/wireless/realtek/rtlwifi/debug.c
@@ -278,8 +278,8 @@ static ssize_t rtl_debugfs_set_write_reg(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';
 
@@ -287,7 +287,7 @@ static ssize_t rtl_debugfs_set_write_reg(struct file *filp,
 	num = sscanf(tmp, "%x %x %x", &addr, &val, &len);
 
 	if (num !=  3)
-		return count;
+		return -EINVAL;
 
 	switch (len) {
 	case 1:
-- 
2.25.1