fs/ntfs3: Do not allow to change label if volume is read-only

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3/super.c

@@ -497,7 +497,12 @@ static ssize_t ntfs3_label_write(struct file *file, const char __user *buffer,
 	int err;
 	struct super_block *sb = pde_data(file_inode(file));
 	ssize_t ret = count;
-	u8 *label = kmalloc(count, GFP_NOFS);
+	u8 *label;
+
+	if (sb_rdonly(sb))
+		return -EROFS;
+
+	label = kmalloc(count, GFP_NOFS);
 
 	if (!label)
 		return -ENOMEM;