pidfs: check for valid ioctl commands

Prior to doing any work, check whether the provided ioctl command is
supported by pidfs.

Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/pidfs.c

@@ -264,6 +264,27 @@ static long pidfd_info(struct task_struct *task, unsigned int cmd, unsigned long
 	return 0;
 }
 
+static bool pidfs_ioctl_valid(unsigned int cmd)
+{
+	switch (cmd) {
+	case FS_IOC_GETVERSION:
+	case PIDFD_GET_CGROUP_NAMESPACE:
+	case PIDFD_GET_INFO:
+	case PIDFD_GET_IPC_NAMESPACE:
+	case PIDFD_GET_MNT_NAMESPACE:
+	case PIDFD_GET_NET_NAMESPACE:
+	case PIDFD_GET_PID_FOR_CHILDREN_NAMESPACE:
+	case PIDFD_GET_TIME_NAMESPACE:
+	case PIDFD_GET_TIME_FOR_CHILDREN_NAMESPACE:
+	case PIDFD_GET_UTS_NAMESPACE:
+	case PIDFD_GET_USER_NAMESPACE:
+	case PIDFD_GET_PID_NAMESPACE:
+		return true;
+	}
+
+	return false;
+}
+
 static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct task_struct *task __free(put_task) = NULL;
@@ -272,6 +293,9 @@ static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct ns_common *ns_common = NULL;
 	struct pid_namespace *pid_ns;
 
+	if (!pidfs_ioctl_valid(cmd))
+		return -ENOIOCTLCMD;
+
 	if (cmd == FS_IOC_GETVERSION) {
 		if (!arg)
 			return -EINVAL;