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 .compat_ioctl = compat_ptr_ioctl, 25 }; 26 27 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 28 { 29 struct inode *inode = d_inode(dentry); 30 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 31 32 return dynamic_dname(buffer, buflen, "%s:[%lu]", 33 ns_ops->name, inode->i_ino); 34 } 35 36 static void ns_prune_dentry(struct dentry *dentry) 37 { 38 struct inode *inode = d_inode(dentry); 39 if (inode) { 40 struct ns_common *ns = inode->i_private; 41 atomic_long_set(&ns->stashed, 0); 42 } 43 } 44 45 const struct dentry_operations ns_dentry_operations = 46 { 47 .d_prune = ns_prune_dentry, 48 .d_delete = always_delete_dentry, 49 .d_dname = ns_dname, 50 }; 51 52 static void nsfs_evict(struct inode *inode) 53 { 54 struct ns_common *ns = inode->i_private; 55 clear_inode(inode); 56 ns->ops->put(ns); 57 } 58 59 static int __ns_get_path(struct path *path, struct ns_common *ns) 60 { 61 struct vfsmount *mnt = nsfs_mnt; 62 struct dentry *dentry; 63 struct inode *inode; 64 unsigned long d; 65 66 rcu_read_lock(); 67 d = atomic_long_read(&ns->stashed); 68 if (!d) 69 goto slow; 70 dentry = (struct dentry *)d; 71 if (!lockref_get_not_dead(&dentry->d_lockref)) 72 goto slow; 73 rcu_read_unlock(); 74 ns->ops->put(ns); 75 got_it: 76 path->mnt = mntget(mnt); 77 path->dentry = dentry; 78 return 0; 79 slow: 80 rcu_read_unlock(); 81 inode = new_inode_pseudo(mnt->mnt_sb); 82 if (!inode) { 83 ns->ops->put(ns); 84 return -ENOMEM; 85 } 86 inode->i_ino = ns->inum; 87 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 88 inode->i_flags |= S_IMMUTABLE; 89 inode->i_mode = S_IFREG | S_IRUGO; 90 inode->i_fop = &ns_file_operations; 91 inode->i_private = ns; 92 93 dentry = d_alloc_anon(mnt->mnt_sb); 94 if (!dentry) { 95 iput(inode); 96 return -ENOMEM; 97 } 98 d_instantiate(dentry, inode); 99 dentry->d_fsdata = (void *)ns->ops; 100 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); 101 if (d) { 102 d_delete(dentry); /* make sure ->d_prune() does nothing */ 103 dput(dentry); 104 cpu_relax(); 105 return -EAGAIN; 106 } 107 goto got_it; 108 } 109 110 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb, 111 void *private_data) 112 { 113 int ret; 114 115 do { 116 struct ns_common *ns = ns_get_cb(private_data); 117 if (!ns) 118 return -ENOENT; 119 ret = __ns_get_path(path, ns); 120 } while (ret == -EAGAIN); 121 122 return ret; 123 } 124 125 struct ns_get_path_task_args { 126 const struct proc_ns_operations *ns_ops; 127 struct task_struct *task; 128 }; 129 130 static struct ns_common *ns_get_path_task(void *private_data) 131 { 132 struct ns_get_path_task_args *args = private_data; 133 134 return args->ns_ops->get(args->task); 135 } 136 137 int ns_get_path(struct path *path, struct task_struct *task, 138 const struct proc_ns_operations *ns_ops) 139 { 140 struct ns_get_path_task_args args = { 141 .ns_ops = ns_ops, 142 .task = task, 143 }; 144 145 return ns_get_path_cb(path, ns_get_path_task, &args); 146 } 147 148 int open_related_ns(struct ns_common *ns, 149 struct ns_common *(*get_ns)(struct ns_common *ns)) 150 { 151 struct path path = {}; 152 struct file *f; 153 int err; 154 int fd; 155 156 fd = get_unused_fd_flags(O_CLOEXEC); 157 if (fd < 0) 158 return fd; 159 160 do { 161 struct ns_common *relative; 162 163 relative = get_ns(ns); 164 if (IS_ERR(relative)) { 165 put_unused_fd(fd); 166 return PTR_ERR(relative); 167 } 168 169 err = __ns_get_path(&path, relative); 170 } while (err == -EAGAIN); 171 172 if (err) { 173 put_unused_fd(fd); 174 return err; 175 } 176 177 f = dentry_open(&path, O_RDONLY, current_cred()); 178 path_put(&path); 179 if (IS_ERR(f)) { 180 put_unused_fd(fd); 181 fd = PTR_ERR(f); 182 } else 183 fd_install(fd, f); 184 185 return fd; 186 } 187 EXPORT_SYMBOL_GPL(open_related_ns); 188 189 static long ns_ioctl(struct file *filp, unsigned int ioctl, 190 unsigned long arg) 191 { 192 struct user_namespace *user_ns; 193 struct ns_common *ns = get_proc_ns(file_inode(filp)); 194 uid_t __user *argp; 195 uid_t uid; 196 197 switch (ioctl) { 198 case NS_GET_USERNS: 199 return open_related_ns(ns, ns_get_owner); 200 case NS_GET_PARENT: 201 if (!ns->ops->get_parent) 202 return -EINVAL; 203 return open_related_ns(ns, ns->ops->get_parent); 204 case NS_GET_NSTYPE: 205 return ns->ops->type; 206 case NS_GET_OWNER_UID: 207 if (ns->ops->type != CLONE_NEWUSER) 208 return -EINVAL; 209 user_ns = container_of(ns, struct user_namespace, ns); 210 argp = (uid_t __user *) arg; 211 uid = from_kuid_munged(current_user_ns(), user_ns->owner); 212 return put_user(uid, argp); 213 default: 214 return -ENOTTY; 215 } 216 } 217 218 int ns_get_name(char *buf, size_t size, struct task_struct *task, 219 const struct proc_ns_operations *ns_ops) 220 { 221 struct ns_common *ns; 222 int res = -ENOENT; 223 const char *name; 224 ns = ns_ops->get(task); 225 if (ns) { 226 name = ns_ops->real_ns_name ? : ns_ops->name; 227 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); 228 ns_ops->put(ns); 229 } 230 return res; 231 } 232 233 bool proc_ns_file(const struct file *file) 234 { 235 return file->f_op == &ns_file_operations; 236 } 237 238 /** 239 * ns_match() - Returns true if current namespace matches dev/ino provided. 240 * @ns: current namespace 241 * @dev: dev_t from nsfs that will be matched against current nsfs 242 * @ino: ino_t from nsfs that will be matched against current nsfs 243 * 244 * Return: true if dev and ino matches the current nsfs. 245 */ 246 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino) 247 { 248 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev); 249 } 250 251 252 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 253 { 254 struct inode *inode = d_inode(dentry); 255 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 256 257 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 258 return 0; 259 } 260 261 static const struct super_operations nsfs_ops = { 262 .statfs = simple_statfs, 263 .evict_inode = nsfs_evict, 264 .show_path = nsfs_show_path, 265 }; 266 267 static int nsfs_init_fs_context(struct fs_context *fc) 268 { 269 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC); 270 if (!ctx) 271 return -ENOMEM; 272 ctx->ops = &nsfs_ops; 273 ctx->dops = &ns_dentry_operations; 274 return 0; 275 } 276 277 static struct file_system_type nsfs = { 278 .name = "nsfs", 279 .init_fs_context = nsfs_init_fs_context, 280 .kill_sb = kill_anon_super, 281 }; 282 283 void __init nsfs_init(void) 284 { 285 nsfs_mnt = kern_mount(&nsfs); 286 if (IS_ERR(nsfs_mnt)) 287 panic("can't set nsfs up\n"); 288 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER; 289 } 290