[PATCH -next] stm class: Switch to memdup_user_nul() helper

[Ruan Jinjie]

Although stm_write() use the kbuf with its count, the last byte of
kbuf is not initialized and there may be problems.

Use memdup_user_nul() helper instead of open-coding to simplify the code
and fix the above issue.

Signed-off-by: Ruan Jinjie <ruanjinjie at huawei.com>
---
 drivers/hwtracing/stm/core.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 534fbefc7f6a..342d0ab6e8ca 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -645,15 +645,9 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf,
 			return err;
 	}
 
-	kbuf = kmalloc(count + 1, GFP_KERNEL);
-	if (!kbuf)
-		return -ENOMEM;
-
-	err = copy_from_user(kbuf, buf, count);
-	if (err) {
-		kfree(kbuf);
-		return -EFAULT;
-	}
+	kbuf = memdup_user_nul(buf, count);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
 
 	pm_runtime_get_sync(&stm->dev);
 
-- 
2.34.1