[PATCH v3] 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 NUL terminated
string which is not necessarily true.

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: 2b42bd58b321 ("staging: r8188eu: introduce new os_dep dir for RTL8188eu driver")
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
Changes in v3:
  -Delete useless printk, modified the commit message and fixes tag.

 drivers/staging/r8188eu/os_dep/ioctl_linux.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/r8188eu/os_dep/ioctl_linux.c b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
index 77728ba78d76..d8c28f279aa0 100644
--- a/drivers/staging/r8188eu/os_dep/ioctl_linux.c
+++ b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
@@ -4247,18 +4247,10 @@ static int rtw_test(
 
 	DBG_88E("+%s\n", __func__);
 	len = wrqu->data.length;
+	pbuf = strndup_user(wrqu->data.pointer, len);
+	if (IS_ERR(pbuf))
+		return PTR_ERR(pbuf);
 
-	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);
-		DBG_88E("%s: copy from user fail!\n", __func__);
-		return -EFAULT;
-	}
 	DBG_88E("%s: string =\"%s\"\n", __func__, pbuf);
 
 	ptmp = (char *)pbuf;
-- 
2.20.1.7.g153144c