// 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/user_namespace.h> #include <linux/nsfs.h> #include <linux/uaccess.h> #include "internal.h" static struct vfsmount *nsfs_mnt; static long ns_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg); static const struct file_operations ns_file_operations = { .llseek = no_llseek, .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_delete = always_delete_dentry, .d_dname = ns_dname, .d_prune = stashed_dentry_prune, }; static void nsfs_evict(struct inode *inode) { struct ns_common *ns = inode->i_private; 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); } int open_related_ns(struct ns_common *ns, struct ns_common *(*get_ns)(struct ns_common *ns)) { struct path path = {}; struct ns_common *relative; struct file *f; int err; int fd; fd = get_unused_fd_flags(O_CLOEXEC); if (fd < 0) return fd; relative = get_ns(ns); if (IS_ERR(relative)) { put_unused_fd(fd); return PTR_ERR(relative); } err = path_from_stashed(&relative->stashed, nsfs_mnt, relative, &path); if (err < 0) { put_unused_fd(fd); return err; } f = dentry_open(&path, O_RDONLY, current_cred()); path_put(&path); if (IS_ERR(f)) { put_unused_fd(fd); fd = PTR_ERR(f); } else fd_install(fd, f); return fd; } EXPORT_SYMBOL_GPL(open_related_ns); static long ns_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { struct user_namespace *user_ns; struct ns_common *ns = get_proc_ns(file_inode(filp)); uid_t __user *argp; uid_t uid; 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->ops->type; case NS_GET_OWNER_UID: if (ns->ops->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); default: return -ENOTTY; } } 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, }; 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; 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, }; static int nsfs_init_fs_context(struct fs_context *fc) { struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC); if (!ctx) return -ENOMEM; ctx->ops = &nsfs_ops; 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; }