[PATCH] stm class: Use memdup_user_nul() to simplify stm_char_policy_set_ioctl()

[Christophe JAILLET]

Instead of hand-writing kzalloc(size+1) + copy_from_user(size), use
memdup_user_nul() that does the same with a few less lines of code.

This also saves a useless zeroing of the allocated memory.

Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
 drivers/hwtracing/stm/core.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 534fbefc7f6a..3ee98208ea8f 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -739,19 +739,11 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
 	if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
 		return -EINVAL;
 
-	/*
-	 * size + 1 to make sure the .id string at the bottom is terminated,
-	 * which is also why memdup_user() is not useful here
-	 */
-	id = kzalloc(size + 1, GFP_KERNEL);
+	/* Make sure the .id string at the bottom is nul terminated. */
+	id = memdup_user_nul(arg, size);
 	if (!id)
 		return -ENOMEM;
 
-	if (copy_from_user(id, arg, size)) {
-		ret = -EFAULT;
-		goto err_free;
-	}
-
 	if (id->__reserved_0 || id->__reserved_1)
 		goto err_free;
 
-- 
2.34.1