Unverified Commit 9b3e1504 authored by Christian Brauner's avatar Christian Brauner
Browse files

pidfs: handle kernels without namespaces cleanly 

The nsproxy structure contains nearly all of the namespaces associated
with a task. When a given namespace type is not supported by this kernel
the rules whether the corresponding pointer in struct nsproxy is NULL or
always init_<ns_type>_ns differ per namespace. Ideally, that wouldn't be
the case and for all namespace types we'd always set it to
init_<ns_type>_ns when the corresponding namespace type isn't supported.

Make sure we handle all namespaces where the pointer in struct nsproxy
can be NULL when the namespace type isn't supported.

Link: https://lore.kernel.org/r/20240722-work-pidfs-e6a83030f63e@brauner


Fixes: 5b08bd40 ("pidfs: allow retrieval of namespace file descriptors") # mainline only
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent f60d38cb

fs/pidfs.c

+42 −23
Original line number Diff line number Diff line
@@ -119,7 +119,7 @@ static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 
	struct task_struct *task __free(put_task) = NULL;

	struct nsproxy *nsp __free(put_nsproxy) = NULL;

	struct pid *pid = pidfd_pid(file);

	struct ns_common *ns_common;

	struct ns_common *ns_common = NULL;



	if (arg)

		return -EINVAL;
@@ -146,54 +146,73 @@ static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 
	switch (cmd) {

	/* Namespaces that hang of nsproxy. */

	case PIDFD_GET_CGROUP_NAMESPACE:

		if (IS_ENABLED(CONFIG_CGROUPS)) {

			get_cgroup_ns(nsp->cgroup_ns);

			ns_common = to_ns_common(nsp->cgroup_ns);

		}

		break;

	case PIDFD_GET_IPC_NAMESPACE:

		if (IS_ENABLED(CONFIG_IPC_NS)) {

			get_ipc_ns(nsp->ipc_ns);

			ns_common = to_ns_common(nsp->ipc_ns);

		}

		break;

	case PIDFD_GET_MNT_NAMESPACE:

		get_mnt_ns(nsp->mnt_ns);

		ns_common = to_ns_common(nsp->mnt_ns);

		break;

	case PIDFD_GET_NET_NAMESPACE:

		if (IS_ENABLED(CONFIG_NET_NS)) {

			ns_common = to_ns_common(nsp->net_ns);

			get_net_ns(ns_common);

		}

		break;

	case PIDFD_GET_PID_FOR_CHILDREN_NAMESPACE:

		if (IS_ENABLED(CONFIG_PID_NS)) {

			get_pid_ns(nsp->pid_ns_for_children);

			ns_common = to_ns_common(nsp->pid_ns_for_children);

		}

		break;

	case PIDFD_GET_TIME_NAMESPACE:

		if (IS_ENABLED(CONFIG_TIME_NS)) {

			get_time_ns(nsp->time_ns);

			ns_common = to_ns_common(nsp->time_ns);

		if (!nsp->time_ns)

			return -EINVAL;

		}

		break;

	case PIDFD_GET_TIME_FOR_CHILDREN_NAMESPACE:

		if (IS_ENABLED(CONFIG_TIME_NS)) {

			get_time_ns(nsp->time_ns_for_children);

			ns_common = to_ns_common(nsp->time_ns_for_children);

		}

		break;

	case PIDFD_GET_UTS_NAMESPACE:

		if (IS_ENABLED(CONFIG_UTS_NS)) {

			get_uts_ns(nsp->uts_ns);

			ns_common = to_ns_common(nsp->uts_ns);

		}

		break;

	/* Namespaces that don't hang of nsproxy. */

	case PIDFD_GET_USER_NAMESPACE:

		if (IS_ENABLED(CONFIG_USER_NS)) {

			rcu_read_lock();

			ns_common = to_ns_common(get_user_ns(task_cred_xxx(task, user_ns)));

			rcu_read_unlock();

		}

		break;

	case PIDFD_GET_PID_NAMESPACE:

		if (IS_ENABLED(CONFIG_PID_NS)) {

			rcu_read_lock();

			ns_common = to_ns_common( get_pid_ns(task_active_pid_ns(task)));

			rcu_read_unlock();

		}

		break;

	default:

		return -ENOIOCTLCMD;

	}



	if (!ns_common)

		return -EOPNOTSUPP;



	/* open_namespace() unconditionally consumes the reference */

	return open_namespace(ns_common);

}