Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 | // SPDX-License-Identifier: GPL-2.0 /* * Author: Andrei Vagin <avagin@openvz.org> * Author: Dmitry Safonov <dima@arista.com> */ #include <linux/time_namespace.h> #include <linux/user_namespace.h> #include <linux/sched/signal.h> #include <linux/sched/task.h> #include <linux/clocksource.h> #include <linux/seq_file.h> #include <linux/proc_ns.h> #include <linux/export.h> #include <linux/time.h> #include <linux/slab.h> #include <linux/cred.h> #include <linux/err.h> #include <linux/mm.h> #include <vdso/datapage.h> ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, struct timens_offsets *ns_offsets) { ktime_t offset; switch (clockid) { case CLOCK_MONOTONIC: offset = timespec64_to_ktime(ns_offsets->monotonic); break; case CLOCK_BOOTTIME: case CLOCK_BOOTTIME_ALARM: offset = timespec64_to_ktime(ns_offsets->boottime); break; default: return tim; } /* * Check that @tim value is in [offset, KTIME_MAX + offset] * and subtract offset. */ if (tim < offset) { /* * User can specify @tim *absolute* value - if it's lesser than * the time namespace's offset - it's already expired. */ tim = 0; } else { tim = ktime_sub(tim, offset); if (unlikely(tim > KTIME_MAX)) tim = KTIME_MAX; } return tim; } static struct ucounts *inc_time_namespaces(struct user_namespace *ns) { return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES); } static void dec_time_namespaces(struct ucounts *ucounts) { dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES); } /** * clone_time_ns - Clone a time namespace * @user_ns: User namespace which owns a new namespace. * @old_ns: Namespace to clone * * Clone @old_ns and set the clone refcount to 1 * * Return: The new namespace or ERR_PTR. */ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns, struct time_namespace *old_ns) { struct time_namespace *ns; struct ucounts *ucounts; int err; err = -ENOSPC; ucounts = inc_time_namespaces(user_ns); if (!ucounts) goto fail; err = -ENOMEM; ns = kmalloc(sizeof(*ns), GFP_KERNEL); if (!ns) goto fail_dec; kref_init(&ns->kref); ns->vvar_page = alloc_page(GFP_KERNEL | __GFP_ZERO); if (!ns->vvar_page) goto fail_free; err = ns_alloc_inum(&ns->ns); if (err) goto fail_free_page; ns->ucounts = ucounts; ns->ns.ops = &timens_operations; ns->user_ns = get_user_ns(user_ns); ns->offsets = old_ns->offsets; ns->frozen_offsets = false; return ns; fail_free_page: __free_page(ns->vvar_page); fail_free: kfree(ns); fail_dec: dec_time_namespaces(ucounts); fail: return ERR_PTR(err); } /** * copy_time_ns - Create timens_for_children from @old_ns * @flags: Cloning flags * @user_ns: User namespace which owns a new namespace. * @old_ns: Namespace to clone * * If CLONE_NEWTIME specified in @flags, creates a new timens_for_children; * adds a refcounter to @old_ns otherwise. * * Return: timens_for_children namespace or ERR_PTR. */ struct time_namespace *copy_time_ns(unsigned long flags, struct user_namespace *user_ns, struct time_namespace *old_ns) { if (!(flags & CLONE_NEWTIME)) return get_time_ns(old_ns); return clone_time_ns(user_ns, old_ns); } static struct timens_offset offset_from_ts(struct timespec64 off) { struct timens_offset ret; ret.sec = off.tv_sec; ret.nsec = off.tv_nsec; return ret; } /* * A time namespace VVAR page has the same layout as the VVAR page which * contains the system wide VDSO data. * * For a normal task the VVAR pages are installed in the normal ordering: * VVAR * PVCLOCK * HVCLOCK * TIMENS <- Not really required * * Now for a timens task the pages are installed in the following order: * TIMENS * PVCLOCK * HVCLOCK * VVAR * * The check for vdso_data->clock_mode is in the unlikely path of * the seq begin magic. So for the non-timens case most of the time * 'seq' is even, so the branch is not taken. * * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check * for vdso_data->clock_mode is a non-issue. The task is spin waiting for the * update to finish and for 'seq' to become even anyway. * * Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which * enforces the time namespace handling path. */ static void timens_setup_vdso_data(struct vdso_data *vdata, struct time_namespace *ns) { struct timens_offset *offset = vdata->offset; struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic); struct timens_offset boottime = offset_from_ts(ns->offsets.boottime); vdata->seq = 1; vdata->clock_mode = VDSO_CLOCKMODE_TIMENS; offset[CLOCK_MONOTONIC] = monotonic; offset[CLOCK_MONOTONIC_RAW] = monotonic; offset[CLOCK_MONOTONIC_COARSE] = monotonic; offset[CLOCK_BOOTTIME] = boottime; offset[CLOCK_BOOTTIME_ALARM] = boottime; } /* * Protects possibly multiple offsets writers racing each other * and tasks entering the namespace. */ static DEFINE_MUTEX(offset_lock); static void timens_set_vvar_page(struct task_struct *task, struct time_namespace *ns) { struct vdso_data *vdata; unsigned int i; if (ns == &init_time_ns) return; /* Fast-path, taken by every task in namespace except the first. */ if (likely(ns->frozen_offsets)) return; mutex_lock(&offset_lock); /* Nothing to-do: vvar_page has been already initialized. */ if (ns->frozen_offsets) goto out; ns->frozen_offsets = true; vdata = arch_get_vdso_data(page_address(ns->vvar_page)); for (i = 0; i < CS_BASES; i++) timens_setup_vdso_data(&vdata[i], ns); out: mutex_unlock(&offset_lock); } void free_time_ns(struct kref *kref) { struct time_namespace *ns; ns = container_of(kref, struct time_namespace, kref); dec_time_namespaces(ns->ucounts); put_user_ns(ns->user_ns); ns_free_inum(&ns->ns); __free_page(ns->vvar_page); kfree(ns); } static struct time_namespace *to_time_ns(struct ns_common *ns) { return container_of(ns, struct time_namespace, ns); } static struct ns_common *timens_get(struct task_struct *task) { struct time_namespace *ns = NULL; struct nsproxy *nsproxy; task_lock(task); nsproxy = task->nsproxy; if (nsproxy) { ns = nsproxy->time_ns; get_time_ns(ns); } task_unlock(task); return ns ? &ns->ns : NULL; } static struct ns_common *timens_for_children_get(struct task_struct *task) { struct time_namespace *ns = NULL; struct nsproxy *nsproxy; task_lock(task); nsproxy = task->nsproxy; if (nsproxy) { ns = nsproxy->time_ns_for_children; get_time_ns(ns); } task_unlock(task); return ns ? &ns->ns : NULL; } static void timens_put(struct ns_common *ns) { put_time_ns(to_time_ns(ns)); } static int timens_install(struct nsproxy *nsproxy, struct ns_common *new) { struct time_namespace *ns = to_time_ns(new); int err; if (!current_is_single_threaded()) return -EUSERS; if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) return -EPERM; timens_set_vvar_page(current, ns); err = vdso_join_timens(current, ns); if (err) return err; get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; get_time_ns(ns); put_time_ns(nsproxy->time_ns_for_children); nsproxy->time_ns_for_children = ns; return 0; } int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) { struct ns_common *nsc = &nsproxy->time_ns_for_children->ns; struct time_namespace *ns = to_time_ns(nsc); int err; /* create_new_namespaces() already incremented the ref counter */ if (nsproxy->time_ns == nsproxy->time_ns_for_children) return 0; timens_set_vvar_page(tsk, ns); err = vdso_join_timens(tsk, ns); if (err) return err; get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; return 0; } static struct user_namespace *timens_owner(struct ns_common *ns) { return to_time_ns(ns)->user_ns; } static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts) { char *clock; switch (clockid) { case CLOCK_BOOTTIME: clock = "boottime"; break; case CLOCK_MONOTONIC: clock = "monotonic"; break; default: clock = "unknown"; break; } seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec); } void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m) { struct ns_common *ns; struct time_namespace *time_ns; ns = timens_for_children_get(p); if (!ns) return; time_ns = to_time_ns(ns); show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic); show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime); put_time_ns(time_ns); } int proc_timens_set_offset(struct file *file, struct task_struct *p, struct proc_timens_offset *offsets, int noffsets) { struct ns_common *ns; struct time_namespace *time_ns; struct timespec64 tp; int i, err; ns = timens_for_children_get(p); if (!ns) return -ESRCH; time_ns = to_time_ns(ns); if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) { put_time_ns(time_ns); return -EPERM; } for (i = 0; i < noffsets; i++) { struct proc_timens_offset *off = &offsets[i]; switch (off->clockid) { case CLOCK_MONOTONIC: ktime_get_ts64(&tp); break; case CLOCK_BOOTTIME: ktime_get_boottime_ts64(&tp); break; default: err = -EINVAL; goto out; } err = -ERANGE; if (off->val.tv_sec > KTIME_SEC_MAX || off->val.tv_sec < -KTIME_SEC_MAX) goto out; tp = timespec64_add(tp, off->val); /* * KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is * still unreachable. */ if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2) goto out; } mutex_lock(&offset_lock); if (time_ns->frozen_offsets) { err = -EACCES; goto out_unlock; } err = 0; /* Don't report errors after this line */ for (i = 0; i < noffsets; i++) { struct proc_timens_offset *off = &offsets[i]; struct timespec64 *offset = NULL; switch (off->clockid) { case CLOCK_MONOTONIC: offset = &time_ns->offsets.monotonic; break; case CLOCK_BOOTTIME: offset = &time_ns->offsets.boottime; break; } *offset = off->val; } out_unlock: mutex_unlock(&offset_lock); out: put_time_ns(time_ns); return err; } const struct proc_ns_operations timens_operations = { .name = "time", .type = CLONE_NEWTIME, .get = timens_get, .put = timens_put, .install = timens_install, .owner = timens_owner, }; const struct proc_ns_operations timens_for_children_operations = { .name = "time_for_children", .real_ns_name = "time", .type = CLONE_NEWTIME, .get = timens_for_children_get, .put = timens_put, .install = timens_install, .owner = timens_owner, }; struct time_namespace init_time_ns = { .kref = KREF_INIT(3), .user_ns = &init_user_ns, .ns.inum = PROC_TIME_INIT_INO, .ns.ops = &timens_operations, .frozen_offsets = true, }; static int __init time_ns_init(void) { return 0; } subsys_initcall(time_ns_init); |