1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/mount.h> 3 #include <linux/pseudo_fs.h> 4 #include <linux/file.h> 5 #include <linux/fs.h> 6 #include <linux/proc_ns.h> 7 #include <linux/magic.h> 8 #include <linux/ktime.h> 9 #include <linux/seq_file.h> 10 #include <linux/user_namespace.h> 11 #include <linux/nsfs.h> 12 #include <linux/uaccess.h> 13 14 static struct vfsmount *nsfs_mnt; 15 16 static long ns_ioctl(struct file *filp, unsigned int ioctl, 17 unsigned long arg); 18 static const struct file_operations ns_file_operations = { 19 .llseek = no_llseek, 20 .unlocked_ioctl = ns_ioctl, 21 }; 22 23 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 24 { 25 struct inode *inode = d_inode(dentry); 26 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 27 28 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", 29 ns_ops->name, inode->i_ino); 30 } 31 32 static void ns_prune_dentry(struct dentry *dentry) 33 { 34 struct inode *inode = d_inode(dentry); 35 if (inode) { 36 struct ns_common *ns = inode->i_private; 37 atomic_long_set(&ns->stashed, 0); 38 } 39 } 40 41 const struct dentry_operations ns_dentry_operations = 42 { 43 .d_prune = ns_prune_dentry, 44 .d_delete = always_delete_dentry, 45 .d_dname = ns_dname, 46 }; 47 48 static void nsfs_evict(struct inode *inode) 49 { 50 struct ns_common *ns = inode->i_private; 51 clear_inode(inode); 52 ns->ops->put(ns); 53 } 54 55 static void *__ns_get_path(struct path *path, struct ns_common *ns) 56 { 57 struct vfsmount *mnt = nsfs_mnt; 58 struct dentry *dentry; 59 struct inode *inode; 60 unsigned long d; 61 62 rcu_read_lock(); 63 d = atomic_long_read(&ns->stashed); 64 if (!d) 65 goto slow; 66 dentry = (struct dentry *)d; 67 if (!lockref_get_not_dead(&dentry->d_lockref)) 68 goto slow; 69 rcu_read_unlock(); 70 ns->ops->put(ns); 71 got_it: 72 path->mnt = mntget(mnt); 73 path->dentry = dentry; 74 return NULL; 75 slow: 76 rcu_read_unlock(); 77 inode = new_inode_pseudo(mnt->mnt_sb); 78 if (!inode) { 79 ns->ops->put(ns); 80 return ERR_PTR(-ENOMEM); 81 } 82 inode->i_ino = ns->inum; 83 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 84 inode->i_flags |= S_IMMUTABLE; 85 inode->i_mode = S_IFREG | S_IRUGO; 86 inode->i_fop = &ns_file_operations; 87 inode->i_private = ns; 88 89 dentry = d_alloc_anon(mnt->mnt_sb); 90 if (!dentry) { 91 iput(inode); 92 return ERR_PTR(-ENOMEM); 93 } 94 d_instantiate(dentry, inode); 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_cb(struct path *path, ns_get_path_helper_t *ns_get_cb, 107 void *private_data) 108 { 109 void *ret; 110 111 do { 112 struct ns_common *ns = ns_get_cb(private_data); 113 if (!ns) 114 return ERR_PTR(-ENOENT); 115 116 ret = __ns_get_path(path, ns); 117 } while (ret == ERR_PTR(-EAGAIN)); 118 119 return ret; 120 } 121 122 struct ns_get_path_task_args { 123 const struct proc_ns_operations *ns_ops; 124 struct task_struct *task; 125 }; 126 127 static struct ns_common *ns_get_path_task(void *private_data) 128 { 129 struct ns_get_path_task_args *args = private_data; 130 131 return args->ns_ops->get(args->task); 132 } 133 134 void *ns_get_path(struct path *path, struct task_struct *task, 135 const struct proc_ns_operations *ns_ops) 136 { 137 struct ns_get_path_task_args args = { 138 .ns_ops = ns_ops, 139 .task = task, 140 }; 141 142 return ns_get_path_cb(path, ns_get_path_task, &args); 143 } 144 145 int open_related_ns(struct ns_common *ns, 146 struct ns_common *(*get_ns)(struct ns_common *ns)) 147 { 148 struct path path = {}; 149 struct file *f; 150 void *err; 151 int fd; 152 153 fd = get_unused_fd_flags(O_CLOEXEC); 154 if (fd < 0) 155 return fd; 156 157 do { 158 struct ns_common *relative; 159 160 relative = get_ns(ns); 161 if (IS_ERR(relative)) { 162 put_unused_fd(fd); 163 return PTR_ERR(relative); 164 } 165 166 err = __ns_get_path(&path, relative); 167 } while (err == ERR_PTR(-EAGAIN)); 168 169 if (IS_ERR(err)) { 170 put_unused_fd(fd); 171 return PTR_ERR(err); 172 } 173 174 f = dentry_open(&path, O_RDONLY, current_cred()); 175 path_put(&path); 176 if (IS_ERR(f)) { 177 put_unused_fd(fd); 178 fd = PTR_ERR(f); 179 } else 180 fd_install(fd, f); 181 182 return fd; 183 } 184 EXPORT_SYMBOL_GPL(open_related_ns); 185 186 static long ns_ioctl(struct file *filp, unsigned int ioctl, 187 unsigned long arg) 188 { 189 struct user_namespace *user_ns; 190 struct ns_common *ns = get_proc_ns(file_inode(filp)); 191 uid_t __user *argp; 192 uid_t uid; 193 194 switch (ioctl) { 195 case NS_GET_USERNS: 196 return open_related_ns(ns, ns_get_owner); 197 case NS_GET_PARENT: 198 if (!ns->ops->get_parent) 199 return -EINVAL; 200 return open_related_ns(ns, ns->ops->get_parent); 201 case NS_GET_NSTYPE: 202 return ns->ops->type; 203 case NS_GET_OWNER_UID: 204 if (ns->ops->type != CLONE_NEWUSER) 205 return -EINVAL; 206 user_ns = container_of(ns, struct user_namespace, ns); 207 argp = (uid_t __user *) arg; 208 uid = from_kuid_munged(current_user_ns(), user_ns->owner); 209 return put_user(uid, argp); 210 default: 211 return -ENOTTY; 212 } 213 } 214 215 int ns_get_name(char *buf, size_t size, struct task_struct *task, 216 const struct proc_ns_operations *ns_ops) 217 { 218 struct ns_common *ns; 219 int res = -ENOENT; 220 const char *name; 221 ns = ns_ops->get(task); 222 if (ns) { 223 name = ns_ops->real_ns_name ? : ns_ops->name; 224 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); 225 ns_ops->put(ns); 226 } 227 return res; 228 } 229 230 struct file *proc_ns_fget(int fd) 231 { 232 struct file *file; 233 234 file = fget(fd); 235 if (!file) 236 return ERR_PTR(-EBADF); 237 238 if (file->f_op != &ns_file_operations) 239 goto out_invalid; 240 241 return file; 242 243 out_invalid: 244 fput(file); 245 return ERR_PTR(-EINVAL); 246 } 247 248 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 249 { 250 struct inode *inode = d_inode(dentry); 251 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 252 253 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 254 return 0; 255 } 256 257 static const struct super_operations nsfs_ops = { 258 .statfs = simple_statfs, 259 .evict_inode = nsfs_evict, 260 .show_path = nsfs_show_path, 261 }; 262 263 static int nsfs_init_fs_context(struct fs_context *fc) 264 { 265 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC); 266 if (!ctx) 267 return -ENOMEM; 268 ctx->ops = &nsfs_ops; 269 ctx->dops = &ns_dentry_operations; 270 return 0; 271 } 272 273 static struct file_system_type nsfs = { 274 .name = "nsfs", 275 .init_fs_context = nsfs_init_fs_context, 276 .kill_sb = kill_anon_super, 277 }; 278 279 void __init nsfs_init(void) 280 { 281 nsfs_mnt = kern_mount(&nsfs); 282 if (IS_ERR(nsfs_mnt)) 283 panic("can't set nsfs up\n"); 284 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER; 285 } 286