1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/mount.h> 3 #include <linux/file.h> 4 #include <linux/fs.h> 5 #include <linux/proc_ns.h> 6 #include <linux/magic.h> 7 #include <linux/ktime.h> 8 #include <linux/seq_file.h> 9 #include <linux/user_namespace.h> 10 #include <linux/nsfs.h> 11 #include <linux/uaccess.h> 12 13 static struct vfsmount *nsfs_mnt; 14 15 static long ns_ioctl(struct file *filp, unsigned int ioctl, 16 unsigned long arg); 17 static const struct file_operations ns_file_operations = { 18 .llseek = no_llseek, 19 .unlocked_ioctl = ns_ioctl, 20 }; 21 22 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 23 { 24 struct inode *inode = d_inode(dentry); 25 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 26 27 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", 28 ns_ops->name, inode->i_ino); 29 } 30 31 static void ns_prune_dentry(struct dentry *dentry) 32 { 33 struct inode *inode = d_inode(dentry); 34 if (inode) { 35 struct ns_common *ns = inode->i_private; 36 atomic_long_set(&ns->stashed, 0); 37 } 38 } 39 40 const struct dentry_operations ns_dentry_operations = 41 { 42 .d_prune = ns_prune_dentry, 43 .d_delete = always_delete_dentry, 44 .d_dname = ns_dname, 45 }; 46 47 static void nsfs_evict(struct inode *inode) 48 { 49 struct ns_common *ns = inode->i_private; 50 clear_inode(inode); 51 ns->ops->put(ns); 52 } 53 54 static void *__ns_get_path(struct path *path, struct ns_common *ns) 55 { 56 struct vfsmount *mnt = nsfs_mnt; 57 struct dentry *dentry; 58 struct inode *inode; 59 unsigned long d; 60 61 rcu_read_lock(); 62 d = atomic_long_read(&ns->stashed); 63 if (!d) 64 goto slow; 65 dentry = (struct dentry *)d; 66 if (!lockref_get_not_dead(&dentry->d_lockref)) 67 goto slow; 68 rcu_read_unlock(); 69 ns->ops->put(ns); 70 got_it: 71 path->mnt = mntget(mnt); 72 path->dentry = dentry; 73 return NULL; 74 slow: 75 rcu_read_unlock(); 76 inode = new_inode_pseudo(mnt->mnt_sb); 77 if (!inode) { 78 ns->ops->put(ns); 79 return ERR_PTR(-ENOMEM); 80 } 81 inode->i_ino = ns->inum; 82 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 83 inode->i_flags |= S_IMMUTABLE; 84 inode->i_mode = S_IFREG | S_IRUGO; 85 inode->i_fop = &ns_file_operations; 86 inode->i_private = ns; 87 88 dentry = d_alloc_pseudo(mnt->mnt_sb, &empty_name); 89 if (!dentry) { 90 iput(inode); 91 return ERR_PTR(-ENOMEM); 92 } 93 d_instantiate(dentry, inode); 94 dentry->d_flags |= DCACHE_RCUACCESS; 95 dentry->d_fsdata = (void *)ns->ops; 96 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); 97 if (d) { 98 d_delete(dentry); /* make sure ->d_prune() does nothing */ 99 dput(dentry); 100 cpu_relax(); 101 return ERR_PTR(-EAGAIN); 102 } 103 goto got_it; 104 } 105 106 void *ns_get_path(struct path *path, struct task_struct *task, 107 const struct proc_ns_operations *ns_ops) 108 { 109 struct ns_common *ns; 110 void *ret; 111 112 again: 113 ns = ns_ops->get(task); 114 if (!ns) 115 return ERR_PTR(-ENOENT); 116 117 ret = __ns_get_path(path, ns); 118 if (IS_ERR(ret) && PTR_ERR(ret) == -EAGAIN) 119 goto again; 120 return ret; 121 } 122 123 int open_related_ns(struct ns_common *ns, 124 struct ns_common *(*get_ns)(struct ns_common *ns)) 125 { 126 struct path path = {}; 127 struct file *f; 128 void *err; 129 int fd; 130 131 fd = get_unused_fd_flags(O_CLOEXEC); 132 if (fd < 0) 133 return fd; 134 135 while (1) { 136 struct ns_common *relative; 137 138 relative = get_ns(ns); 139 if (IS_ERR(relative)) { 140 put_unused_fd(fd); 141 return PTR_ERR(relative); 142 } 143 144 err = __ns_get_path(&path, relative); 145 if (IS_ERR(err) && PTR_ERR(err) == -EAGAIN) 146 continue; 147 break; 148 } 149 if (IS_ERR(err)) { 150 put_unused_fd(fd); 151 return PTR_ERR(err); 152 } 153 154 f = dentry_open(&path, O_RDONLY, current_cred()); 155 path_put(&path); 156 if (IS_ERR(f)) { 157 put_unused_fd(fd); 158 fd = PTR_ERR(f); 159 } else 160 fd_install(fd, f); 161 162 return fd; 163 } 164 165 static long ns_ioctl(struct file *filp, unsigned int ioctl, 166 unsigned long arg) 167 { 168 struct user_namespace *user_ns; 169 struct ns_common *ns = get_proc_ns(file_inode(filp)); 170 uid_t __user *argp; 171 uid_t uid; 172 173 switch (ioctl) { 174 case NS_GET_USERNS: 175 return open_related_ns(ns, ns_get_owner); 176 case NS_GET_PARENT: 177 if (!ns->ops->get_parent) 178 return -EINVAL; 179 return open_related_ns(ns, ns->ops->get_parent); 180 case NS_GET_NSTYPE: 181 return ns->ops->type; 182 case NS_GET_OWNER_UID: 183 if (ns->ops->type != CLONE_NEWUSER) 184 return -EINVAL; 185 user_ns = container_of(ns, struct user_namespace, ns); 186 argp = (uid_t __user *) arg; 187 uid = from_kuid_munged(current_user_ns(), user_ns->owner); 188 return put_user(uid, argp); 189 default: 190 return -ENOTTY; 191 } 192 } 193 194 int ns_get_name(char *buf, size_t size, struct task_struct *task, 195 const struct proc_ns_operations *ns_ops) 196 { 197 struct ns_common *ns; 198 int res = -ENOENT; 199 const char *name; 200 ns = ns_ops->get(task); 201 if (ns) { 202 name = ns_ops->real_ns_name ? : ns_ops->name; 203 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); 204 ns_ops->put(ns); 205 } 206 return res; 207 } 208 209 struct file *proc_ns_fget(int fd) 210 { 211 struct file *file; 212 213 file = fget(fd); 214 if (!file) 215 return ERR_PTR(-EBADF); 216 217 if (file->f_op != &ns_file_operations) 218 goto out_invalid; 219 220 return file; 221 222 out_invalid: 223 fput(file); 224 return ERR_PTR(-EINVAL); 225 } 226 227 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 228 { 229 struct inode *inode = d_inode(dentry); 230 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 231 232 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 233 return 0; 234 } 235 236 static const struct super_operations nsfs_ops = { 237 .statfs = simple_statfs, 238 .evict_inode = nsfs_evict, 239 .show_path = nsfs_show_path, 240 }; 241 static struct dentry *nsfs_mount(struct file_system_type *fs_type, 242 int flags, const char *dev_name, void *data) 243 { 244 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops, 245 &ns_dentry_operations, NSFS_MAGIC); 246 } 247 static struct file_system_type nsfs = { 248 .name = "nsfs", 249 .mount = nsfs_mount, 250 .kill_sb = kill_anon_super, 251 }; 252 253 void __init nsfs_init(void) 254 { 255 nsfs_mnt = kern_mount(&nsfs); 256 if (IS_ERR(nsfs_mnt)) 257 panic("can't set nsfs up\n"); 258 nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER; 259 } 260