// SPDX-License-Identifier: GPL-2.0
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/proc_ns.h>
#include <linux/magic.h>
#include <linux/ktime.h>
#include <linux/seq_file.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/nsfs.h>
#include <linux/uaccess.h>
#include <linux/mnt_namespace.h>
#include <linux/ipc_namespace.h>
#include <linux/time_namespace.h>
#include <linux/utsname.h>
#include <linux/exportfs.h>
#include <linux/nstree.h>
#include <net/net_namespace.h>

#include "mount.h"
#include "internal.h"

static struct vfsmount *nsfs_mnt;

static struct path nsfs_root_path = {};

void nsfs_get_root(struct path *path)
{
        *path = nsfs_root_path;
        path_get(path);
}

static long ns_ioctl(struct file *filp, unsigned int ioctl,
                        unsigned long arg);
static const struct file_operations ns_file_operations = {
        .unlocked_ioctl = ns_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
};

static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
{
        struct inode *inode = d_inode(dentry);
        struct ns_common *ns = inode->i_private;
        const struct proc_ns_operations *ns_ops = ns->ops;

        return dynamic_dname(buffer, buflen, "%s:[%lu]",
                ns_ops->name, inode->i_ino);
}

const struct dentry_operations ns_dentry_operations = {
        .d_dname        = ns_dname,
        .d_prune        = stashed_dentry_prune,
};

static void nsfs_evict(struct inode *inode)
{
        struct ns_common *ns = inode->i_private;

        __ns_ref_active_put(ns);
        clear_inode(inode);
        ns->ops->put(ns);
}

int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
                     void *private_data)
{
        struct ns_common *ns;

        ns = ns_get_cb(private_data);
        if (!ns)
                return -ENOENT;

        return path_from_stashed(&ns->stashed, nsfs_mnt, ns, path);
}

struct ns_get_path_task_args {
        const struct proc_ns_operations *ns_ops;
        struct task_struct *task;
};

static struct ns_common *ns_get_path_task(void *private_data)
{
        struct ns_get_path_task_args *args = private_data;

        return args->ns_ops->get(args->task);
}

int ns_get_path(struct path *path, struct task_struct *task,
                  const struct proc_ns_operations *ns_ops)
{
        struct ns_get_path_task_args args = {
                .ns_ops = ns_ops,
                .task   = task,
        };

        return ns_get_path_cb(path, ns_get_path_task, &args);
}

struct file *open_namespace_file(struct ns_common *ns)
{
        struct path path __free(path_put) = {};
        int err;

        /* call first to consume reference */
        err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
        if (err < 0)
                return ERR_PTR(err);

        return dentry_open(&path, O_RDONLY, current_cred());
}

/**
 * open_namespace - open a namespace
 * @ns: the namespace to open
 *
 * This will consume a reference to @ns indendent of success or failure.
 *
 * Return: A file descriptor on success or a negative error code on failure.
 */
int open_namespace(struct ns_common *ns)
{
        struct path path __free(path_put) = {};
        int err;

        /* call first to consume reference */
        err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
        if (err < 0)
                return err;

        return FD_ADD(O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
}

int open_related_ns(struct ns_common *ns,
                   struct ns_common *(*get_ns)(struct ns_common *ns))
{
        struct ns_common *relative;

        relative = get_ns(ns);
        if (IS_ERR(relative))
                return PTR_ERR(relative);

        return open_namespace(relative);
}
EXPORT_SYMBOL_GPL(open_related_ns);

static int copy_ns_info_to_user(const struct mnt_namespace *mnt_ns,
                                struct mnt_ns_info __user *uinfo, size_t usize,
                                struct mnt_ns_info *kinfo)
{
        /*
         * If userspace and the kernel have the same struct size it can just
         * be copied. If userspace provides an older struct, only the bits that
         * userspace knows about will be copied. If userspace provides a new
         * struct, only the bits that the kernel knows aobut will be copied and
         * the size value will be set to the size the kernel knows about.
         */
        kinfo->size             = min(usize, sizeof(*kinfo));
        kinfo->mnt_ns_id        = mnt_ns->ns.ns_id;
        kinfo->nr_mounts        = READ_ONCE(mnt_ns->nr_mounts);
        /* Subtract the root mount of the mount namespace. */
        if (kinfo->nr_mounts)
                kinfo->nr_mounts--;

        if (copy_to_user(uinfo, kinfo, kinfo->size))
                return -EFAULT;

        return 0;
}

static bool nsfs_ioctl_valid(unsigned int cmd)
{
        switch (cmd) {
        case NS_GET_USERNS:
        case NS_GET_PARENT:
        case NS_GET_NSTYPE:
        case NS_GET_OWNER_UID:
        case NS_GET_MNTNS_ID:
        case NS_GET_PID_FROM_PIDNS:
        case NS_GET_TGID_FROM_PIDNS:
        case NS_GET_PID_IN_PIDNS:
        case NS_GET_TGID_IN_PIDNS:
        case NS_GET_ID:
                return true;
        }

        /* Extensible ioctls require some extra handling. */
        switch (_IOC_NR(cmd)) {
        case _IOC_NR(NS_MNT_GET_INFO):
                return extensible_ioctl_valid(cmd, NS_MNT_GET_INFO, MNT_NS_INFO_SIZE_VER0);
        case _IOC_NR(NS_MNT_GET_NEXT):
                return extensible_ioctl_valid(cmd, NS_MNT_GET_NEXT, MNT_NS_INFO_SIZE_VER0);
        case _IOC_NR(NS_MNT_GET_PREV):
                return extensible_ioctl_valid(cmd, NS_MNT_GET_PREV, MNT_NS_INFO_SIZE_VER0);
        }

        return false;
}

static bool may_use_nsfs_ioctl(unsigned int cmd)
{
        switch (_IOC_NR(cmd)) {
        case _IOC_NR(NS_MNT_GET_NEXT):
                fallthrough;
        case _IOC_NR(NS_MNT_GET_PREV):
                return may_see_all_namespaces();
        }
        return true;
}

static long ns_ioctl(struct file *filp, unsigned int ioctl,
                        unsigned long arg)
{
        struct user_namespace *user_ns;
        struct pid_namespace *pid_ns;
        struct task_struct *tsk;
        struct ns_common *ns;
        struct mnt_namespace *mnt_ns;
        bool previous = false;
        uid_t __user *argp;
        uid_t uid;
        int ret;

        if (!nsfs_ioctl_valid(ioctl))
                return -ENOIOCTLCMD;
        if (!may_use_nsfs_ioctl(ioctl))
                return -EPERM;

        ns = get_proc_ns(file_inode(filp));
        switch (ioctl) {
        case NS_GET_USERNS:
                return open_related_ns(ns, ns_get_owner);
        case NS_GET_PARENT:
                if (!ns->ops->get_parent)
                        return -EINVAL;
                return open_related_ns(ns, ns->ops->get_parent);
        case NS_GET_NSTYPE:
                return ns->ns_type;
        case NS_GET_OWNER_UID:
                if (ns->ns_type != CLONE_NEWUSER)
                        return -EINVAL;
                user_ns = container_of(ns, struct user_namespace, ns);
                argp = (uid_t __user *) arg;
                uid = from_kuid_munged(current_user_ns(), user_ns->owner);
                return put_user(uid, argp);
        case NS_GET_PID_FROM_PIDNS:
                fallthrough;
        case NS_GET_TGID_FROM_PIDNS:
                fallthrough;
        case NS_GET_PID_IN_PIDNS:
                fallthrough;
        case NS_GET_TGID_IN_PIDNS: {
                if (ns->ns_type != CLONE_NEWPID)
                        return -EINVAL;

                ret = -ESRCH;
                pid_ns = container_of(ns, struct pid_namespace, ns);

                guard(rcu)();

                if (ioctl == NS_GET_PID_IN_PIDNS ||
                    ioctl == NS_GET_TGID_IN_PIDNS)
                        tsk = find_task_by_vpid(arg);
                else
                        tsk = find_task_by_pid_ns(arg, pid_ns);
                if (!tsk)
                        break;

                switch (ioctl) {
                case NS_GET_PID_FROM_PIDNS:
                        ret = task_pid_vnr(tsk);
                        break;
                case NS_GET_TGID_FROM_PIDNS:
                        ret = task_tgid_vnr(tsk);
                        break;
                case NS_GET_PID_IN_PIDNS:
                        ret = task_pid_nr_ns(tsk, pid_ns);
                        break;
                case NS_GET_TGID_IN_PIDNS:
                        ret = task_tgid_nr_ns(tsk, pid_ns);
                        break;
                default:
                        ret = 0;
                        break;
                }

                if (!ret)
                        ret = -ESRCH;
                return ret;
        }
        case NS_GET_MNTNS_ID:
                if (ns->ns_type != CLONE_NEWNS)
                        return -EINVAL;
                fallthrough;
        case NS_GET_ID: {
                __u64 __user *idp;
                __u64 id;

                idp = (__u64 __user *)arg;
                id = ns->ns_id;
                return put_user(id, idp);
        }
        }

        /* extensible ioctls */
        switch (_IOC_NR(ioctl)) {
        case _IOC_NR(NS_MNT_GET_INFO): {
                struct mnt_ns_info kinfo = {};
                struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
                size_t usize = _IOC_SIZE(ioctl);

                if (ns->ns_type != CLONE_NEWNS)
                        return -EINVAL;

                if (!uinfo)
                        return -EINVAL;

                if (usize < MNT_NS_INFO_SIZE_VER0)
                        return -EINVAL;

                return copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
        }
        case _IOC_NR(NS_MNT_GET_PREV):
                previous = true;
                fallthrough;
        case _IOC_NR(NS_MNT_GET_NEXT): {
                struct mnt_ns_info kinfo = {};
                struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
                struct path path __free(path_put) = {};
                size_t usize = _IOC_SIZE(ioctl);

                if (ns->ns_type != CLONE_NEWNS)
                        return -EINVAL;

                if (usize < MNT_NS_INFO_SIZE_VER0)
                        return -EINVAL;

                mnt_ns = get_sequential_mnt_ns(to_mnt_ns(ns), previous);
                if (IS_ERR(mnt_ns))
                        return PTR_ERR(mnt_ns);

                ns = to_ns_common(mnt_ns);
                /* Transfer ownership of @mnt_ns reference to @path. */
                ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
                if (ret)
                        return ret;

                FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
                if (fdf.err)
                        return fdf.err;
                /*
                 * If @uinfo is passed return all information about the
                 * mount namespace as well.
                 */
                ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
                if (ret)
                        return ret;
                ret = fd_publish(fdf);
                break;
        }
        default:
                ret = -ENOTTY;
        }

        return ret;
}

int ns_get_name(char *buf, size_t size, struct task_struct *task,
                        const struct proc_ns_operations *ns_ops)
{
        struct ns_common *ns;
        int res = -ENOENT;
        const char *name;
        ns = ns_ops->get(task);
        if (ns) {
                name = ns_ops->real_ns_name ? : ns_ops->name;
                res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
                ns_ops->put(ns);
        }
        return res;
}

bool proc_ns_file(const struct file *file)
{
        return file->f_op == &ns_file_operations;
}

/**
 * ns_match() - Returns true if current namespace matches dev/ino provided.
 * @ns: current namespace
 * @dev: dev_t from nsfs that will be matched against current nsfs
 * @ino: ino_t from nsfs that will be matched against current nsfs
 *
 * Return: true if dev and ino matches the current nsfs.
 */
bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
{
        return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
}


static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        const struct ns_common *ns = inode->i_private;
        const struct proc_ns_operations *ns_ops = ns->ops;

        seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
        return 0;
}

static const struct super_operations nsfs_ops = {
        .statfs = simple_statfs,
        .evict_inode = nsfs_evict,
        .show_path = nsfs_show_path,
        .drop_inode = inode_just_drop,
};

static int nsfs_init_inode(struct inode *inode, void *data)
{
        struct ns_common *ns = data;

        inode->i_private = data;
        inode->i_mode |= S_IRUGO;
        inode->i_fop = &ns_file_operations;
        inode->i_ino = ns->inum;

        /*
         * Bring the namespace subtree back to life if we have to. This
         * can happen when e.g., all processes using a network namespace
         * and all namespace files or namespace file bind-mounts have
         * died but there are still sockets pinning it. The SIOCGSKNS
         * ioctl on such a socket will resurrect the relevant namespace
         * subtree.
         */
        __ns_ref_active_get(ns);
        return 0;
}

static void nsfs_put_data(void *data)
{
        struct ns_common *ns = data;
        ns->ops->put(ns);
}

static const struct stashed_operations nsfs_stashed_ops = {
        .init_inode = nsfs_init_inode,
        .put_data = nsfs_put_data,
};

#define NSFS_FID_SIZE_U32_VER0 (NSFS_FILE_HANDLE_SIZE_VER0 / sizeof(u32))
#define NSFS_FID_SIZE_U32_LATEST (NSFS_FILE_HANDLE_SIZE_LATEST / sizeof(u32))

static int nsfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
                          struct inode *parent)
{
        struct nsfs_file_handle *fid = (struct nsfs_file_handle *)fh;
        struct ns_common *ns = inode->i_private;
        int len = *max_len;

        if (parent)
                return FILEID_INVALID;

        if (len < NSFS_FID_SIZE_U32_VER0) {
                *max_len = NSFS_FID_SIZE_U32_LATEST;
                return FILEID_INVALID;
        } else if (len > NSFS_FID_SIZE_U32_LATEST) {
                *max_len = NSFS_FID_SIZE_U32_LATEST;
        }

        fid->ns_id      = ns->ns_id;
        fid->ns_type    = ns->ns_type;
        fid->ns_inum    = inode->i_ino;
        return FILEID_NSFS;
}

bool is_current_namespace(struct ns_common *ns)
{
        switch (ns->ns_type) {
#ifdef CONFIG_CGROUPS
        case CLONE_NEWCGROUP:
                return current_in_namespace(to_cg_ns(ns));
#endif
#ifdef CONFIG_IPC_NS
        case CLONE_NEWIPC:
                return current_in_namespace(to_ipc_ns(ns));
#endif
        case CLONE_NEWNS:
                return current_in_namespace(to_mnt_ns(ns));
#ifdef CONFIG_NET_NS
        case CLONE_NEWNET:
                return current_in_namespace(to_net_ns(ns));
#endif
#ifdef CONFIG_PID_NS
        case CLONE_NEWPID:
                return current_in_namespace(to_pid_ns(ns));
#endif
#ifdef CONFIG_TIME_NS
        case CLONE_NEWTIME:
                return current_in_namespace(to_time_ns(ns));
#endif
#ifdef CONFIG_USER_NS
        case CLONE_NEWUSER:
                return current_in_namespace(to_user_ns(ns));
#endif
#ifdef CONFIG_UTS_NS
        case CLONE_NEWUTS:
                return current_in_namespace(to_uts_ns(ns));
#endif
        default:
                VFS_WARN_ON_ONCE(true);
                return false;
        }
}

static struct dentry *nsfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
                                        int fh_len, int fh_type)
{
        struct path path __free(path_put) = {};
        struct nsfs_file_handle *fid = (struct nsfs_file_handle *)fh;
        struct user_namespace *owning_ns = NULL;
        struct ns_common *ns;
        int ret;

        if (fh_len < NSFS_FID_SIZE_U32_VER0)
                return NULL;

        /* Check that any trailing bytes are zero. */
        if ((fh_len > NSFS_FID_SIZE_U32_LATEST) &&
            memchr_inv((void *)fid + NSFS_FID_SIZE_U32_LATEST, 0,
                       fh_len - NSFS_FID_SIZE_U32_LATEST))
                return NULL;

        switch (fh_type) {
        case FILEID_NSFS:
                break;
        default:
                return NULL;
        }

        if (!fid->ns_id)
                return NULL;
        /* Either both are set or both are unset. */
        if (!fid->ns_inum != !fid->ns_type)
                return NULL;

        scoped_guard(rcu) {
                ns = ns_tree_lookup_rcu(fid->ns_id, fid->ns_type);
                if (!ns)
                        return NULL;

                VFS_WARN_ON_ONCE(ns->ns_id != fid->ns_id);

                if (fid->ns_inum && (fid->ns_inum != ns->inum))
                        return NULL;
                if (fid->ns_type && (fid->ns_type != ns->ns_type))
                        return NULL;

                /*
                 * This is racy because we're not actually taking an
                 * active reference. IOW, it could happen that the
                 * namespace becomes inactive after this check.
                 * We don't care because nsfs_init_inode() will just
                 * resurrect the relevant namespace tree for us. If it
                 * has been active here we just allow it's resurrection.
                 * We could try to take an active reference here and
                 * then drop it again. But really, why bother.
                 */
                if (!ns_get_unless_inactive(ns))
                        return NULL;
        }

        switch (ns->ns_type) {
#ifdef CONFIG_CGROUPS
        case CLONE_NEWCGROUP:
                if (!current_in_namespace(to_cg_ns(ns)))
                        owning_ns = to_cg_ns(ns)->user_ns;
                break;
#endif
#ifdef CONFIG_IPC_NS
        case CLONE_NEWIPC:
                if (!current_in_namespace(to_ipc_ns(ns)))
                        owning_ns = to_ipc_ns(ns)->user_ns;
                break;
#endif
        case CLONE_NEWNS:
                if (!current_in_namespace(to_mnt_ns(ns)))
                        owning_ns = to_mnt_ns(ns)->user_ns;
                break;
#ifdef CONFIG_NET_NS
        case CLONE_NEWNET:
                if (!current_in_namespace(to_net_ns(ns)))
                        owning_ns = to_net_ns(ns)->user_ns;
                break;
#endif
#ifdef CONFIG_PID_NS
        case CLONE_NEWPID:
                if (!current_in_namespace(to_pid_ns(ns))) {
                        owning_ns = to_pid_ns(ns)->user_ns;
                } else if (!READ_ONCE(to_pid_ns(ns)->child_reaper)) {
                        ns->ops->put(ns);
                        return ERR_PTR(-EPERM);
                }
                break;
#endif
#ifdef CONFIG_TIME_NS
        case CLONE_NEWTIME:
                if (!current_in_namespace(to_time_ns(ns)))
                        owning_ns = to_time_ns(ns)->user_ns;
                break;
#endif
#ifdef CONFIG_USER_NS
        case CLONE_NEWUSER:
                if (!current_in_namespace(to_user_ns(ns)))
                        owning_ns = to_user_ns(ns);
                break;
#endif
#ifdef CONFIG_UTS_NS
        case CLONE_NEWUTS:
                if (!current_in_namespace(to_uts_ns(ns)))
                        owning_ns = to_uts_ns(ns)->user_ns;
                break;
#endif
        default:
                return ERR_PTR(-EOPNOTSUPP);
        }

        if (owning_ns && !may_see_all_namespaces()) {
                ns->ops->put(ns);
                return ERR_PTR(-EPERM);
        }

        /* path_from_stashed() unconditionally consumes the reference. */
        ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
        if (ret)
                return ERR_PTR(ret);

        return no_free_ptr(path.dentry);
}

static int nsfs_export_permission(struct handle_to_path_ctx *ctx,
                                   unsigned int oflags)
{
        /* nsfs_fh_to_dentry() performs all permission checks. */
        return 0;
}

static struct file *nsfs_export_open(const struct path *path, unsigned int oflags)
{
        return file_open_root(path, "", oflags, 0);
}

static const struct export_operations nsfs_export_operations = {
        .encode_fh      = nsfs_encode_fh,
        .fh_to_dentry   = nsfs_fh_to_dentry,
        .open           = nsfs_export_open,
        .permission     = nsfs_export_permission,
};

static int nsfs_init_fs_context(struct fs_context *fc)
{
        struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
        if (!ctx)
                return -ENOMEM;
        fc->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
        ctx->s_d_flags |= DCACHE_DONTCACHE;
        ctx->ops = &nsfs_ops;
        ctx->eops = &nsfs_export_operations;
        ctx->dops = &ns_dentry_operations;
        fc->s_fs_info = (void *)&nsfs_stashed_ops;
        return 0;
}

static struct file_system_type nsfs = {
        .name = "nsfs",
        .init_fs_context = nsfs_init_fs_context,
        .kill_sb = kill_anon_super,
};

void __init nsfs_init(void)
{
        nsfs_mnt = kern_mount(&nsfs);
        if (IS_ERR(nsfs_mnt))
                panic("can't set nsfs up\n");
        nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
        nsfs_root_path.mnt = nsfs_mnt;
        nsfs_root_path.dentry = nsfs_mnt->mnt_root;
}

void nsproxy_ns_active_get(struct nsproxy *ns)
{
        ns_ref_active_get(ns->mnt_ns);
        ns_ref_active_get(ns->uts_ns);
        ns_ref_active_get(ns->ipc_ns);
        ns_ref_active_get(ns->pid_ns_for_children);
        ns_ref_active_get(ns->cgroup_ns);
        ns_ref_active_get(ns->net_ns);
        ns_ref_active_get(ns->time_ns);
        ns_ref_active_get(ns->time_ns_for_children);
}

void nsproxy_ns_active_put(struct nsproxy *ns)
{
        ns_ref_active_put(ns->mnt_ns);
        ns_ref_active_put(ns->uts_ns);
        ns_ref_active_put(ns->ipc_ns);
        ns_ref_active_put(ns->pid_ns_for_children);
        ns_ref_active_put(ns->cgroup_ns);
        ns_ref_active_put(ns->net_ns);
        ns_ref_active_put(ns->time_ns);
        ns_ref_active_put(ns->time_ns_for_children);
}