[PATCH RESEND 2/2] stm class: Replace kzalloc + copy_from_user with memdup_user_nul

[Thorsten Blum <thorsten.blum@linux.dev>]

Replace kzalloc() followed by copy_from_user() with memdup_user_nul() to
simplify and improve stm_char_policy_set_ioctl(). Remove the obsolete
comment.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/hwtracing/stm/core.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 5834f796e86b..335bcf749214 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -733,18 +733,9 @@ 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);
-	if (!id)
-		return -ENOMEM;
-
-	if (copy_from_user(id, arg, size)) {
-		ret = -EFAULT;
-		goto err_free;
-	}
+	id = memdup_user_nul(arg, size);
+	if (IS_ERR(id))
+		return PTR_ERR(id);
 
 	if (id->__reserved_0 || id->__reserved_1)
 		goto err_free;
-- 
2.51.1