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_fs.h> 7 #include <linux/proc_ns.h> 8 #include <linux/magic.h> 9 #include <linux/ktime.h> 10 #include <linux/seq_file.h> 11 #include <linux/user_namespace.h> 12 #include <linux/nsfs.h> 13 #include <linux/uaccess.h> 14 15 #include "internal.h" 16 17 static struct vfsmount *nsfs_mnt; 18 19 static long ns_ioctl(struct file *filp, unsigned int ioctl, 20 unsigned long arg); 21 static const struct file_operations ns_file_operations = { 22 .llseek = no_llseek, 23 .unlocked_ioctl = ns_ioctl, 24 }; 25 26 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 27 { 28 struct inode *inode = d_inode(dentry); 29 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 30 31 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", 32 ns_ops->name, inode->i_ino); 33 } 34 35 static void ns_prune_dentry(struct dentry *dentry) 36 { 37 struct inode *inode = d_inode(dentry); 38 if (inode) { 39 struct ns_common *ns = inode->i_private; 40 atomic_long_set(&ns->stashed, 0); 41 } 42 } 43 44 const struct dentry_operations ns_dentry_operations = 45 { 46 .d_prune = ns_prune_dentry, 47 .d_delete = always_delete_dentry, 48 .d_dname = ns_dname, 49 }; 50 51 static void nsfs_evict(struct inode *inode) 52 { 53 struct ns_common *ns = inode->i_private; 54 clear_inode(inode); 55 ns->ops->put(ns); 56 } 57 58 static int __ns_get_path(struct path *path, struct ns_common *ns) 59 { 60 struct vfsmount *mnt = nsfs_mnt; 61 struct dentry *dentry; 62 struct inode *inode; 63 unsigned long d; 64 65 rcu_read_lock(); 66 d = atomic_long_read(&ns->stashed); 67 if (!d) 68 goto slow; 69 dentry = (struct dentry *)d; 70 if (!lockref_get_not_dead(&dentry->d_lockref)) 71 goto slow; 72 rcu_read_unlock(); 73 ns->ops->put(ns); 74 got_it: 75 path->mnt = mntget(mnt); 76 path->dentry = dentry; 77 return 0; 78 slow: 79 rcu_read_unlock(); 80 inode = new_inode_pseudo(mnt->mnt_sb); 81 if (!inode) { 82 ns->ops->put(ns); 83 return -ENOMEM; 84 } 85 inode->i_ino = ns->inum; 86 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 87 inode->i_flags |= S_IMMUTABLE; 88 inode->i_mode = S_IFREG | S_IRUGO; 89 inode->i_fop = &ns_file_operations; 90 inode->i_private = ns; 91 92 dentry = d_alloc_anon(mnt->mnt_sb); 93 if (!dentry) { 94 iput(inode); 95 return -ENOMEM; 96 } 97 d_instantiate(dentry, inode); 98 dentry->d_fsdata = (void *)ns->ops; 99 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); 100 if (d) { 101 d_delete(dentry); /* make sure ->d_prune() does nothing */ 102 dput(dentry); 103 cpu_relax(); 104 return -EAGAIN; 105 } 106 goto got_it; 107 } 108 109 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb, 110 void *private_data) 111 { 112 int ret; 113 114 do { 115 struct ns_common *ns = ns_get_cb(private_data); 116 if (!ns) 117 return -ENOENT; 118 ret = __ns_get_path(path, ns); 119 } while (ret == -EAGAIN); 120 121 return ret; 122 } 123 124 struct ns_get_path_task_args { 125 const struct proc_ns_operations *ns_ops; 126 struct task_struct *task; 127 }; 128 129 static struct ns_common *ns_get_path_task(void *private_data) 130 { 131 struct ns_get_path_task_args *args = private_data; 132 133 return args->ns_ops->get(args->task); 134 } 135 136 int ns_get_path(struct path *path, struct task_struct *task, 137 const struct proc_ns_operations *ns_ops) 138 { 139 struct ns_get_path_task_args args = { 140 .ns_ops = ns_ops, 141 .task = task, 142 }; 143 144 return ns_get_path_cb(path, ns_get_path_task, &args); 145 } 146 147 int open_related_ns(struct ns_common *ns, 148 struct ns_common *(*get_ns)(struct ns_common *ns)) 149 { 150 struct path path = {}; 151 struct file *f; 152 int err; 153 int fd; 154 155 fd = get_unused_fd_flags(O_CLOEXEC); 156 if (fd < 0) 157 return fd; 158 159 do { 160 struct ns_common *relative; 161 162 relative = get_ns(ns); 163 if (IS_ERR(relative)) { 164 put_unused_fd(fd); 165 return PTR_ERR(relative); 166 } 167 168 err = __ns_get_path(&path, relative); 169 } while (err == -EAGAIN); 170 171 if (err) { 172 put_unused_fd(fd); 173 return err; 174 } 175 176 f = dentry_open(&path, O_RDONLY, current_cred()); 177 path_put(&path); 178 if (IS_ERR(f)) { 179 put_unused_fd(fd); 180 fd = PTR_ERR(f); 181 } else 182 fd_install(fd, f); 183 184 return fd; 185 } 186 EXPORT_SYMBOL_GPL(open_related_ns); 187 188 static long ns_ioctl(struct file *filp, unsigned int ioctl, 189 unsigned long arg) 190 { 191 struct user_namespace *user_ns; 192 struct ns_common *ns = get_proc_ns(file_inode(filp)); 193 uid_t __user *argp; 194 uid_t uid; 195 196 switch (ioctl) { 197 case NS_GET_USERNS: 198 return open_related_ns(ns, ns_get_owner); 199 case NS_GET_PARENT: 200 if (!ns->ops->get_parent) 201 return -EINVAL; 202 return open_related_ns(ns, ns->ops->get_parent); 203 case NS_GET_NSTYPE: 204 return ns->ops->type; 205 case NS_GET_OWNER_UID: 206 if (ns->ops->type != CLONE_NEWUSER) 207 return -EINVAL; 208 user_ns = container_of(ns, struct user_namespace, ns); 209 argp = (uid_t __user *) arg; 210 uid = from_kuid_munged(current_user_ns(), user_ns->owner); 211 return put_user(uid, argp); 212 default: 213 return -ENOTTY; 214 } 215 } 216 217 int ns_get_name(char *buf, size_t size, struct task_struct *task, 218 const struct proc_ns_operations *ns_ops) 219 { 220 struct ns_common *ns; 221 int res = -ENOENT; 222 const char *name; 223 ns = ns_ops->get(task); 224 if (ns) { 225 name = ns_ops->real_ns_name ? : ns_ops->name; 226 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); 227 ns_ops->put(ns); 228 } 229 return res; 230 } 231 232 struct file *proc_ns_fget(int fd) 233 { 234 struct file *file; 235 236 file = fget(fd); 237 if (!file) 238 return ERR_PTR(-EBADF); 239 240 if (file->f_op != &ns_file_operations) 241 goto out_invalid; 242 243 return file; 244 245 out_invalid: 246 fput(file); 247 return ERR_PTR(-EINVAL); 248 } 249 250 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 251 { 252 struct inode *inode = d_inode(dentry); 253 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 254 255 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 256 return 0; 257 } 258 259 static const struct super_operations nsfs_ops = { 260 .statfs = simple_statfs, 261 .evict_inode = nsfs_evict, 262 .show_path = nsfs_show_path, 263 }; 264 265 static int nsfs_init_fs_context(struct fs_context *fc) 266 { 267 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC); 268 if (!ctx) 269 return -ENOMEM; 270 ctx->ops = &nsfs_ops; 271 ctx->dops = &ns_dentry_operations; 272 return 0; 273 } 274 275 static struct file_system_type nsfs = { 276 .name = "nsfs", 277 .init_fs_context = nsfs_init_fs_context, 278 .kill_sb = kill_anon_super, 279 }; 280 281 void __init nsfs_init(void) 282 { 283 nsfs_mnt = kern_mount(&nsfs); 284 if (IS_ERR(nsfs_mnt)) 285 panic("can't set nsfs up\n"); 286 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER; 287 } 288