f2fs: Use struct_size() to improve f2fs_acl_clone()

Use struct_size() to calculate the number of bytes to allocate for a
cloned acl.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: toblux

fs/f2fs/acl.c

@@ -296,9 +296,8 @@ static struct posix_acl *f2fs_acl_clone(const struct posix_acl *acl,
 	struct posix_acl *clone = NULL;
 
 	if (acl) {
-		int size = sizeof(struct posix_acl) + acl->a_count *
-				sizeof(struct posix_acl_entry);
-		clone = kmemdup(acl, size, flags);
+		clone = kmemdup(acl, struct_size(acl, a_entries, acl->a_count),
+				flags);
 		if (clone)
 			refcount_set(&clone->a_refcount, 1);
 	}