[PATCH v2] staging: r8188eu: Use strndup_user instead of kmalloc/copy_from_user

[Jiapeng Chong <jiapeng.chong@linux.alibaba.com>]

This code assumes that the user is going to give us a NULL terminated
string which is not necessarily true.  The original code was buggy too.

Fix following coccicheck warning:

./drivers/staging/r8188eu/os_dep/ioctl_linux.c:4253:8-15: WARNING
opportunity for memdup_user.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Fixes: 7bdedfef085b ("staging: r8188eu: Remove mp, a.k.a. manufacturing process, code")
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
Changes in v2:
  -For the follow advice:https://lore.kernel.org/lkml/20211210083010.GM1956@kadam/

 drivers/staging/r8188eu/os_dep/ioctl_linux.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/r8188eu/os_dep/ioctl_linux.c b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
index 56adfe4087a8..5d26dffe5c0d 100644
--- a/drivers/staging/r8188eu/os_dep/ioctl_linux.c
+++ b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
@@ -4250,17 +4250,12 @@ static int rtw_test(
 	DBG_88E("+%s\n", __func__);
 	len = wrqu->data.length;
 
-	pbuf = kzalloc(len, GFP_KERNEL);
-	if (!pbuf) {
-		DBG_88E("%s: no memory!\n", __func__);
-		return -ENOMEM;
-	}
-
-	if (copy_from_user(pbuf, wrqu->data.pointer, len)) {
-		kfree(pbuf);
+	pbuf = strndup_user(wrqu->data.pointer, len);
+	if (IS_ERR(pbuf)) {
 		DBG_88E("%s: copy from user fail!\n", __func__);
-		return -EFAULT;
+		return PTR_ERR(pbuf);
 	}
+
 	DBG_88E("%s: string =\"%s\"\n", __func__, pbuf);
 
 	ptmp = (char *)pbuf;
-- 
2.20.1.7.g153144c