1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Author: Andrei Vagin <avagin@openvz.org> 4 * Author: Dmitry Safonov <dima@arista.com> 5 */ 6 7 #include <linux/time_namespace.h> 8 #include <linux/user_namespace.h> 9 #include <linux/sched/signal.h> 10 #include <linux/sched/task.h> 11 #include <linux/clocksource.h> 12 #include <linux/seq_file.h> 13 #include <linux/proc_ns.h> 14 #include <linux/export.h> 15 #include <linux/time.h> 16 #include <linux/slab.h> 17 #include <linux/cred.h> 18 #include <linux/err.h> 19 #include <linux/mm.h> 20 21 #include <vdso/datapage.h> 22 23 ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, 24 struct timens_offsets *ns_offsets) 25 { 26 ktime_t offset; 27 28 switch (clockid) { 29 case CLOCK_MONOTONIC: 30 offset = timespec64_to_ktime(ns_offsets->monotonic); 31 break; 32 case CLOCK_BOOTTIME: 33 case CLOCK_BOOTTIME_ALARM: 34 offset = timespec64_to_ktime(ns_offsets->boottime); 35 break; 36 default: 37 return tim; 38 } 39 40 /* 41 * Check that @tim value is in [offset, KTIME_MAX + offset] 42 * and subtract offset. 43 */ 44 if (tim < offset) { 45 /* 46 * User can specify @tim *absolute* value - if it's lesser than 47 * the time namespace's offset - it's already expired. 48 */ 49 tim = 0; 50 } else { 51 tim = ktime_sub(tim, offset); 52 if (unlikely(tim > KTIME_MAX)) 53 tim = KTIME_MAX; 54 } 55 56 return tim; 57 } 58 59 static struct ucounts *inc_time_namespaces(struct user_namespace *ns) 60 { 61 return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES); 62 } 63 64 static void dec_time_namespaces(struct ucounts *ucounts) 65 { 66 dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES); 67 } 68 69 /** 70 * clone_time_ns - Clone a time namespace 71 * @user_ns: User namespace which owns a new namespace. 72 * @old_ns: Namespace to clone 73 * 74 * Clone @old_ns and set the clone refcount to 1 75 * 76 * Return: The new namespace or ERR_PTR. 77 */ 78 static struct time_namespace *clone_time_ns(struct user_namespace *user_ns, 79 struct time_namespace *old_ns) 80 { 81 struct time_namespace *ns; 82 struct ucounts *ucounts; 83 int err; 84 85 err = -ENOSPC; 86 ucounts = inc_time_namespaces(user_ns); 87 if (!ucounts) 88 goto fail; 89 90 err = -ENOMEM; 91 ns = kmalloc(sizeof(*ns), GFP_KERNEL); 92 if (!ns) 93 goto fail_dec; 94 95 refcount_set(&ns->ns.count, 1); 96 97 ns->vvar_page = alloc_page(GFP_KERNEL | __GFP_ZERO); 98 if (!ns->vvar_page) 99 goto fail_free; 100 101 err = ns_alloc_inum(&ns->ns); 102 if (err) 103 goto fail_free_page; 104 105 ns->ucounts = ucounts; 106 ns->ns.ops = &timens_operations; 107 ns->user_ns = get_user_ns(user_ns); 108 ns->offsets = old_ns->offsets; 109 ns->frozen_offsets = false; 110 return ns; 111 112 fail_free_page: 113 __free_page(ns->vvar_page); 114 fail_free: 115 kfree(ns); 116 fail_dec: 117 dec_time_namespaces(ucounts); 118 fail: 119 return ERR_PTR(err); 120 } 121 122 /** 123 * copy_time_ns - Create timens_for_children from @old_ns 124 * @flags: Cloning flags 125 * @user_ns: User namespace which owns a new namespace. 126 * @old_ns: Namespace to clone 127 * 128 * If CLONE_NEWTIME specified in @flags, creates a new timens_for_children; 129 * adds a refcounter to @old_ns otherwise. 130 * 131 * Return: timens_for_children namespace or ERR_PTR. 132 */ 133 struct time_namespace *copy_time_ns(unsigned long flags, 134 struct user_namespace *user_ns, struct time_namespace *old_ns) 135 { 136 if (!(flags & CLONE_NEWTIME)) 137 return get_time_ns(old_ns); 138 139 return clone_time_ns(user_ns, old_ns); 140 } 141 142 static struct timens_offset offset_from_ts(struct timespec64 off) 143 { 144 struct timens_offset ret; 145 146 ret.sec = off.tv_sec; 147 ret.nsec = off.tv_nsec; 148 149 return ret; 150 } 151 152 /* 153 * A time namespace VVAR page has the same layout as the VVAR page which 154 * contains the system wide VDSO data. 155 * 156 * For a normal task the VVAR pages are installed in the normal ordering: 157 * VVAR 158 * PVCLOCK 159 * HVCLOCK 160 * TIMENS <- Not really required 161 * 162 * Now for a timens task the pages are installed in the following order: 163 * TIMENS 164 * PVCLOCK 165 * HVCLOCK 166 * VVAR 167 * 168 * The check for vdso_data->clock_mode is in the unlikely path of 169 * the seq begin magic. So for the non-timens case most of the time 170 * 'seq' is even, so the branch is not taken. 171 * 172 * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check 173 * for vdso_data->clock_mode is a non-issue. The task is spin waiting for the 174 * update to finish and for 'seq' to become even anyway. 175 * 176 * Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which 177 * enforces the time namespace handling path. 178 */ 179 static void timens_setup_vdso_data(struct vdso_data *vdata, 180 struct time_namespace *ns) 181 { 182 struct timens_offset *offset = vdata->offset; 183 struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic); 184 struct timens_offset boottime = offset_from_ts(ns->offsets.boottime); 185 186 vdata->seq = 1; 187 vdata->clock_mode = VDSO_CLOCKMODE_TIMENS; 188 offset[CLOCK_MONOTONIC] = monotonic; 189 offset[CLOCK_MONOTONIC_RAW] = monotonic; 190 offset[CLOCK_MONOTONIC_COARSE] = monotonic; 191 offset[CLOCK_BOOTTIME] = boottime; 192 offset[CLOCK_BOOTTIME_ALARM] = boottime; 193 } 194 195 /* 196 * Protects possibly multiple offsets writers racing each other 197 * and tasks entering the namespace. 198 */ 199 static DEFINE_MUTEX(offset_lock); 200 201 static void timens_set_vvar_page(struct task_struct *task, 202 struct time_namespace *ns) 203 { 204 struct vdso_data *vdata; 205 unsigned int i; 206 207 if (ns == &init_time_ns) 208 return; 209 210 /* Fast-path, taken by every task in namespace except the first. */ 211 if (likely(ns->frozen_offsets)) 212 return; 213 214 mutex_lock(&offset_lock); 215 /* Nothing to-do: vvar_page has been already initialized. */ 216 if (ns->frozen_offsets) 217 goto out; 218 219 ns->frozen_offsets = true; 220 vdata = arch_get_vdso_data(page_address(ns->vvar_page)); 221 222 for (i = 0; i < CS_BASES; i++) 223 timens_setup_vdso_data(&vdata[i], ns); 224 225 out: 226 mutex_unlock(&offset_lock); 227 } 228 229 void free_time_ns(struct time_namespace *ns) 230 { 231 dec_time_namespaces(ns->ucounts); 232 put_user_ns(ns->user_ns); 233 ns_free_inum(&ns->ns); 234 __free_page(ns->vvar_page); 235 kfree(ns); 236 } 237 238 static struct time_namespace *to_time_ns(struct ns_common *ns) 239 { 240 return container_of(ns, struct time_namespace, ns); 241 } 242 243 static struct ns_common *timens_get(struct task_struct *task) 244 { 245 struct time_namespace *ns = NULL; 246 struct nsproxy *nsproxy; 247 248 task_lock(task); 249 nsproxy = task->nsproxy; 250 if (nsproxy) { 251 ns = nsproxy->time_ns; 252 get_time_ns(ns); 253 } 254 task_unlock(task); 255 256 return ns ? &ns->ns : NULL; 257 } 258 259 static struct ns_common *timens_for_children_get(struct task_struct *task) 260 { 261 struct time_namespace *ns = NULL; 262 struct nsproxy *nsproxy; 263 264 task_lock(task); 265 nsproxy = task->nsproxy; 266 if (nsproxy) { 267 ns = nsproxy->time_ns_for_children; 268 get_time_ns(ns); 269 } 270 task_unlock(task); 271 272 return ns ? &ns->ns : NULL; 273 } 274 275 static void timens_put(struct ns_common *ns) 276 { 277 put_time_ns(to_time_ns(ns)); 278 } 279 280 void timens_commit(struct task_struct *tsk, struct time_namespace *ns) 281 { 282 timens_set_vvar_page(tsk, ns); 283 vdso_join_timens(tsk, ns); 284 } 285 286 static int timens_install(struct nsset *nsset, struct ns_common *new) 287 { 288 struct nsproxy *nsproxy = nsset->nsproxy; 289 struct time_namespace *ns = to_time_ns(new); 290 291 if (!current_is_single_threaded()) 292 return -EUSERS; 293 294 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 295 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) 296 return -EPERM; 297 298 get_time_ns(ns); 299 put_time_ns(nsproxy->time_ns); 300 nsproxy->time_ns = ns; 301 302 get_time_ns(ns); 303 put_time_ns(nsproxy->time_ns_for_children); 304 nsproxy->time_ns_for_children = ns; 305 return 0; 306 } 307 308 void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) 309 { 310 struct ns_common *nsc = &nsproxy->time_ns_for_children->ns; 311 struct time_namespace *ns = to_time_ns(nsc); 312 313 /* create_new_namespaces() already incremented the ref counter */ 314 if (nsproxy->time_ns == nsproxy->time_ns_for_children) 315 return; 316 317 get_time_ns(ns); 318 put_time_ns(nsproxy->time_ns); 319 nsproxy->time_ns = ns; 320 321 timens_commit(tsk, ns); 322 } 323 324 static struct user_namespace *timens_owner(struct ns_common *ns) 325 { 326 return to_time_ns(ns)->user_ns; 327 } 328 329 static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts) 330 { 331 char *clock; 332 333 switch (clockid) { 334 case CLOCK_BOOTTIME: 335 clock = "boottime"; 336 break; 337 case CLOCK_MONOTONIC: 338 clock = "monotonic"; 339 break; 340 default: 341 clock = "unknown"; 342 break; 343 } 344 seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec); 345 } 346 347 void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m) 348 { 349 struct ns_common *ns; 350 struct time_namespace *time_ns; 351 352 ns = timens_for_children_get(p); 353 if (!ns) 354 return; 355 time_ns = to_time_ns(ns); 356 357 show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic); 358 show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime); 359 put_time_ns(time_ns); 360 } 361 362 int proc_timens_set_offset(struct file *file, struct task_struct *p, 363 struct proc_timens_offset *offsets, int noffsets) 364 { 365 struct ns_common *ns; 366 struct time_namespace *time_ns; 367 struct timespec64 tp; 368 int i, err; 369 370 ns = timens_for_children_get(p); 371 if (!ns) 372 return -ESRCH; 373 time_ns = to_time_ns(ns); 374 375 if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) { 376 put_time_ns(time_ns); 377 return -EPERM; 378 } 379 380 for (i = 0; i < noffsets; i++) { 381 struct proc_timens_offset *off = &offsets[i]; 382 383 switch (off->clockid) { 384 case CLOCK_MONOTONIC: 385 ktime_get_ts64(&tp); 386 break; 387 case CLOCK_BOOTTIME: 388 ktime_get_boottime_ts64(&tp); 389 break; 390 default: 391 err = -EINVAL; 392 goto out; 393 } 394 395 err = -ERANGE; 396 397 if (off->val.tv_sec > KTIME_SEC_MAX || 398 off->val.tv_sec < -KTIME_SEC_MAX) 399 goto out; 400 401 tp = timespec64_add(tp, off->val); 402 /* 403 * KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is 404 * still unreachable. 405 */ 406 if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2) 407 goto out; 408 } 409 410 mutex_lock(&offset_lock); 411 if (time_ns->frozen_offsets) { 412 err = -EACCES; 413 goto out_unlock; 414 } 415 416 err = 0; 417 /* Don't report errors after this line */ 418 for (i = 0; i < noffsets; i++) { 419 struct proc_timens_offset *off = &offsets[i]; 420 struct timespec64 *offset = NULL; 421 422 switch (off->clockid) { 423 case CLOCK_MONOTONIC: 424 offset = &time_ns->offsets.monotonic; 425 break; 426 case CLOCK_BOOTTIME: 427 offset = &time_ns->offsets.boottime; 428 break; 429 } 430 431 *offset = off->val; 432 } 433 434 out_unlock: 435 mutex_unlock(&offset_lock); 436 out: 437 put_time_ns(time_ns); 438 439 return err; 440 } 441 442 const struct proc_ns_operations timens_operations = { 443 .name = "time", 444 .type = CLONE_NEWTIME, 445 .get = timens_get, 446 .put = timens_put, 447 .install = timens_install, 448 .owner = timens_owner, 449 }; 450 451 const struct proc_ns_operations timens_for_children_operations = { 452 .name = "time_for_children", 453 .real_ns_name = "time", 454 .type = CLONE_NEWTIME, 455 .get = timens_for_children_get, 456 .put = timens_put, 457 .install = timens_install, 458 .owner = timens_owner, 459 }; 460 461 struct time_namespace init_time_ns = { 462 .ns.count = REFCOUNT_INIT(3), 463 .user_ns = &init_user_ns, 464 .ns.inum = PROC_TIME_INIT_INO, 465 .ns.ops = &timens_operations, 466 .frozen_offsets = true, 467 }; 468 469 static int __init time_ns_init(void) 470 { 471 return 0; 472 } 473 subsys_initcall(time_ns_init); 474