tools/testing/selftests/pidfd/pidfd_test.c

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2
   3 #define _GNU_SOURCE
   4 #include <errno.h>
   5 #include <fcntl.h>
   6 #include <linux/types.h>
   7 #include <pthread.h>
   8 #include <sched.h>
   9 #include <signal.h>
  10 #include <stdio.h>
  11 #include <stdbool.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <syscall.h>
  15 #include <sys/epoll.h>
  16 #include <sys/mman.h>
  17 #include <sys/mount.h>
  18 #include <sys/wait.h>
  19 #include <time.h>
  20 #include <unistd.h>
  21
  22 #include "pidfd.h"
  23 #include "../kselftest.h"
  24
  25 #define str(s) _str(s)
  26 #define _str(s) #s
  27 #define CHILD_THREAD_MIN_WAIT 3 /* seconds */
  28
  29 #define MAX_EVENTS 5
  30
  31 static bool have_pidfd_send_signal;
  32
  33 static pid_t pidfd_clone(int flags, int *pidfd, int (*fn)(void *))
  34 {
  35         size_t stack_size = 1024;
  36         char *stack[1024] = { 0 };
  37
  38 #ifdef __ia64__
  39         return __clone2(fn, stack, stack_size, flags | SIGCHLD, NULL, pidfd);
  40 #else
  41         return clone(fn, stack + stack_size, flags | SIGCHLD, NULL, pidfd);
  42 #endif
  43 }
  44
  45 static int signal_received;
  46
  47 static void set_signal_received_on_sigusr1(int sig)
  48 {
  49         if (sig == SIGUSR1)
  50                 signal_received = 1;
  51 }
  52
  53 /*
  54  * Straightforward test to see whether pidfd_send_signal() works is to send
  55  * a signal to ourself.
  56  */
  57 static int test_pidfd_send_signal_simple_success(void)
  58 {
  59         int pidfd, ret;
  60         const char *test_name = "pidfd_send_signal send SIGUSR1";
  61
  62         if (!have_pidfd_send_signal) {
  63                 ksft_test_result_skip(
  64                         "%s test: pidfd_send_signal() syscall not supported\n",
  65                         test_name);
  66                 return 0;
  67         }
  68
  69         pidfd = open("/proc/self", O_DIRECTORY | O_CLOEXEC);
  70         if (pidfd < 0)
  71                 ksft_exit_fail_msg(
  72                         "%s test: Failed to open process file descriptor\n",
  73                         test_name);
  74
  75         signal(SIGUSR1, set_signal_received_on_sigusr1);
  76
  77         ret = sys_pidfd_send_signal(pidfd, SIGUSR1, NULL, 0);
  78         close(pidfd);
  79         if (ret < 0)
  80                 ksft_exit_fail_msg("%s test: Failed to send signal\n",
  81                                    test_name);
  82
  83         if (signal_received != 1)
  84                 ksft_exit_fail_msg("%s test: Failed to receive signal\n",
  85                                    test_name);
  86
  87         signal_received = 0;
  88         ksft_test_result_pass("%s test: Sent signal\n", test_name);
  89         return 0;
  90 }
  91
  92 static int test_pidfd_send_signal_exited_fail(void)
  93 {
  94         int pidfd, ret, saved_errno;
  95         char buf[256];
  96         pid_t pid;
  97         const char *test_name = "pidfd_send_signal signal exited process";
  98
  99         if (!have_pidfd_send_signal) {
 100                 ksft_test_result_skip(
 101                         "%s test: pidfd_send_signal() syscall not supported\n",
 102                         test_name);
 103                 return 0;
 104         }
 105
 106         pid = fork();
 107         if (pid < 0)
 108                 ksft_exit_fail_msg("%s test: Failed to create new process\n",
 109                                    test_name);
 110
 111         if (pid == 0)
 112                 _exit(EXIT_SUCCESS);
 113
 114         snprintf(buf, sizeof(buf), "/proc/%d", pid);
 115
 116         pidfd = open(buf, O_DIRECTORY | O_CLOEXEC);
 117
 118         (void)wait_for_pid(pid);
 119
 120         if (pidfd < 0)
 121                 ksft_exit_fail_msg(
 122                         "%s test: Failed to open process file descriptor\n",
 123                         test_name);
 124
 125         ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0);
 126         saved_errno = errno;
 127         close(pidfd);
 128         if (ret == 0)
 129                 ksft_exit_fail_msg(
 130                         "%s test: Managed to send signal to process even though it should have failed\n",
 131                         test_name);
 132
 133         if (saved_errno != ESRCH)
 134                 ksft_exit_fail_msg(
 135                         "%s test: Expected to receive ESRCH as errno value but received %d instead\n",
 136                         test_name, saved_errno);
 137
 138         ksft_test_result_pass("%s test: Failed to send signal as expected\n",
 139                               test_name);
 140         return 0;
 141 }
 142
 143 /*
 144  * Maximum number of cycles we allow. This is equivalent to PID_MAX_DEFAULT.
 145  * If users set a higher limit or we have cycled PIDFD_MAX_DEFAULT number of
 146  * times then we skip the test to not go into an infinite loop or block for a
 147  * long time.
 148  */
 149 #define PIDFD_MAX_DEFAULT 0x8000
 150
 151 static int test_pidfd_send_signal_recycled_pid_fail(void)
 152 {
 153         int i, ret;
 154         pid_t pid1;
 155         const char *test_name = "pidfd_send_signal signal recycled pid";
 156
 157         if (!have_pidfd_send_signal) {
 158                 ksft_test_result_skip(
 159                         "%s test: pidfd_send_signal() syscall not supported\n",
 160                         test_name);
 161                 return 0;
 162         }
 163
 164         ret = unshare(CLONE_NEWPID);
 165         if (ret < 0) {
 166                 if (errno == EPERM) {
 167                         ksft_test_result_skip("%s test: Unsharing pid namespace not permitted\n",
 168                                               test_name);
 169                         return 0;
 170                 }
 171                 ksft_exit_fail_msg("%s test: Failed to unshare pid namespace\n",
 172                                    test_name);
 173         }
 174
 175         ret = unshare(CLONE_NEWNS);
 176         if (ret < 0) {
 177                 if (errno == EPERM) {
 178                         ksft_test_result_skip("%s test: Unsharing mount namespace not permitted\n",
 179                                               test_name);
 180                         return 0;
 181                 }
 182                 ksft_exit_fail_msg("%s test: Failed to unshare mount namespace\n",
 183                                    test_name);
 184         }
 185
 186         ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
 187         if (ret < 0)
 188                 ksft_exit_fail_msg("%s test: Failed to remount / private\n",
 189                                    test_name);
 190
 191         /* pid 1 in new pid namespace */
 192         pid1 = fork();
 193         if (pid1 < 0)
 194                 ksft_exit_fail_msg("%s test: Failed to create new process\n",
 195                                    test_name);
 196
 197         if (pid1 == 0) {
 198                 char buf[256];
 199                 pid_t pid2;
 200                 int pidfd = -1;
 201
 202                 (void)umount2("/proc", MNT_DETACH);
 203                 ret = mount("proc", "/proc", "proc", 0, NULL);
 204                 if (ret < 0)
 205                         _exit(PIDFD_ERROR);
 206
 207                 /* grab pid PID_RECYCLE */
 208                 for (i = 0; i <= PIDFD_MAX_DEFAULT; i++) {
 209                         pid2 = fork();
 210                         if (pid2 < 0)
 211                                 _exit(PIDFD_ERROR);
 212
 213                         if (pid2 == 0)
 214                                 _exit(PIDFD_PASS);
 215
 216                         if (pid2 == PID_RECYCLE) {
 217                                 snprintf(buf, sizeof(buf), "/proc/%d", pid2);
 218                                 ksft_print_msg("pid to recycle is %d\n", pid2);
 219                                 pidfd = open(buf, O_DIRECTORY | O_CLOEXEC);
 220                         }
 221
 222                         if (wait_for_pid(pid2))
 223                                 _exit(PIDFD_ERROR);
 224
 225                         if (pid2 >= PID_RECYCLE)
 226                                 break;
 227                 }
 228
 229                 /*
 230                  * We want to be as predictable as we can so if we haven't been
 231                  * able to grab pid PID_RECYCLE skip the test.
 232                  */
 233                 if (pid2 != PID_RECYCLE) {
 234                         /* skip test */
 235                         close(pidfd);
 236                         _exit(PIDFD_SKIP);
 237                 }
 238
 239                 if (pidfd < 0)
 240                         _exit(PIDFD_ERROR);
 241
 242                 for (i = 0; i <= PIDFD_MAX_DEFAULT; i++) {
 243                         char c;
 244                         int pipe_fds[2];
 245                         pid_t recycled_pid;
 246                         int child_ret = PIDFD_PASS;
 247
 248                         ret = pipe2(pipe_fds, O_CLOEXEC);
 249                         if (ret < 0)
 250                                 _exit(PIDFD_ERROR);
 251
 252                         recycled_pid = fork();
 253                         if (recycled_pid < 0)
 254                                 _exit(PIDFD_ERROR);
 255
 256                         if (recycled_pid == 0) {
 257                                 close(pipe_fds[1]);
 258                                 (void)read(pipe_fds[0], &c, 1);
 259                                 close(pipe_fds[0]);
 260
 261                                 _exit(PIDFD_PASS);
 262                         }
 263
 264                         /*
 265                          * Stop the child so we can inspect whether we have
 266                          * recycled pid PID_RECYCLE.
 267                          */
 268                         close(pipe_fds[0]);
 269                         ret = kill(recycled_pid, SIGSTOP);
 270                         close(pipe_fds[1]);
 271                         if (ret) {
 272                                 (void)wait_for_pid(recycled_pid);
 273                                 _exit(PIDFD_ERROR);
 274                         }
 275
 276                         /*
 277                          * We have recycled the pid. Try to signal it. This
 278                          * needs to fail since this is a different process than
 279                          * the one the pidfd refers to.
 280                          */
 281                         if (recycled_pid == PID_RECYCLE) {
 282                                 ret = sys_pidfd_send_signal(pidfd, SIGCONT,
 283                                                             NULL, 0);
 284                                 if (ret && errno == ESRCH)
 285                                         child_ret = PIDFD_XFAIL;
 286                                 else
 287                                         child_ret = PIDFD_FAIL;
 288                         }
 289
 290                         /* let the process move on */
 291                         ret = kill(recycled_pid, SIGCONT);
 292                         if (ret)
 293                                 (void)kill(recycled_pid, SIGKILL);
 294
 295                         if (wait_for_pid(recycled_pid))
 296                                 _exit(PIDFD_ERROR);
 297
 298                         switch (child_ret) {
 299                         case PIDFD_FAIL:
 300                                 /* fallthrough */
 301                         case PIDFD_XFAIL:
 302                                 _exit(child_ret);
 303                         case PIDFD_PASS:
 304                                 break;
 305                         default:
 306                                 /* not reached */
 307                                 _exit(PIDFD_ERROR);
 308                         }
 309
 310                         /*
 311                          * If the user set a custom pid_max limit we could be
 312                          * in the millions.
 313                          * Skip the test in this case.
 314                          */
 315                         if (recycled_pid > PIDFD_MAX_DEFAULT)
 316                                 _exit(PIDFD_SKIP);
 317                 }
 318
 319                 /* failed to recycle pid */
 320                 _exit(PIDFD_SKIP);
 321         }
 322
 323         ret = wait_for_pid(pid1);
 324         switch (ret) {
 325         case PIDFD_FAIL:
 326                 ksft_exit_fail_msg(
 327                         "%s test: Managed to signal recycled pid %d\n",
 328                         test_name, PID_RECYCLE);
 329         case PIDFD_PASS:
 330                 ksft_exit_fail_msg("%s test: Failed to recycle pid %d\n",
 331                                    test_name, PID_RECYCLE);
 332         case PIDFD_SKIP:
 333                 ksft_print_msg("%s test: Skipping test\n", test_name);
 334                 ret = 0;
 335                 break;
 336         case PIDFD_XFAIL:
 337                 ksft_test_result_pass(
 338                         "%s test: Failed to signal recycled pid as expected\n",
 339                         test_name);
 340                 ret = 0;
 341                 break;
 342         default /* PIDFD_ERROR */:
 343                 ksft_exit_fail_msg("%s test: Error while running tests\n",
 344                                    test_name);
 345         }
 346
 347         return ret;
 348 }
 349
 350 static int test_pidfd_send_signal_syscall_support(void)
 351 {
 352         int pidfd, ret;
 353         const char *test_name = "pidfd_send_signal check for support";
 354
 355         pidfd = open("/proc/self", O_DIRECTORY | O_CLOEXEC);
 356         if (pidfd < 0)
 357                 ksft_exit_fail_msg(
 358                         "%s test: Failed to open process file descriptor\n",
 359                         test_name);
 360
 361         ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0);
 362         if (ret < 0) {
 363                 if (errno == ENOSYS) {
 364                         ksft_test_result_skip(
 365                                 "%s test: pidfd_send_signal() syscall not supported\n",
 366                                 test_name);
 367                         return 0;
 368                 }
 369                 ksft_exit_fail_msg("%s test: Failed to send signal\n",
 370                                    test_name);
 371         }
 372
 373         have_pidfd_send_signal = true;
 374         close(pidfd);
 375         ksft_test_result_pass(
 376                 "%s test: pidfd_send_signal() syscall is supported. Tests can be executed\n",
 377                 test_name);
 378         return 0;
 379 }
 380
 381 static void *test_pidfd_poll_exec_thread(void *priv)
 382 {
 383         ksft_print_msg("Child Thread: starting. pid %d tid %d ; and sleeping\n",
 384                         getpid(), syscall(SYS_gettid));
 385         ksft_print_msg("Child Thread: doing exec of sleep\n");
 386
 387         execl("/bin/sleep", "sleep", str(CHILD_THREAD_MIN_WAIT), (char *)NULL);
 388
 389         ksft_print_msg("Child Thread: DONE. pid %d tid %d\n",
 390                         getpid(), syscall(SYS_gettid));
 391         return NULL;
 392 }
 393
 394 static void poll_pidfd(const char *test_name, int pidfd)
 395 {
 396         int c;
 397         int epoll_fd = epoll_create1(EPOLL_CLOEXEC);
 398         struct epoll_event event, events[MAX_EVENTS];
 399
 400         if (epoll_fd == -1)
 401                 ksft_exit_fail_msg("%s test: Failed to create epoll file descriptor "
 402                                    "(errno %d)\n",
 403                                    test_name, errno);
 404
 405         event.events = EPOLLIN;
 406         event.data.fd = pidfd;
 407
 408         if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, pidfd, &event)) {
 409                 ksft_exit_fail_msg("%s test: Failed to add epoll file descriptor "
 410                                    "(errno %d)\n",
 411                                    test_name, errno);
 412         }
 413
 414         c = epoll_wait(epoll_fd, events, MAX_EVENTS, 5000);
 415         if (c != 1 || !(events[0].events & EPOLLIN))
 416                 ksft_exit_fail_msg("%s test: Unexpected epoll_wait result (c=%d, events=%x) ",
 417                                    "(errno %d)\n",
 418                                    test_name, c, events[0].events, errno);
 419
 420         close(epoll_fd);
 421         return;
 422
 423 }
 424
 425 static int child_poll_exec_test(void *args)
 426 {
 427         pthread_t t1;
 428
 429         ksft_print_msg("Child (pidfd): starting. pid %d tid %d\n", getpid(),
 430                         syscall(SYS_gettid));
 431         pthread_create(&t1, NULL, test_pidfd_poll_exec_thread, NULL);
 432         /*
 433          * Exec in the non-leader thread will destroy the leader immediately.
 434          * If the wait in the parent returns too soon, the test fails.
 435          */
 436         while (1)
 437                 sleep(1);
 438 }
 439
 440 static void test_pidfd_poll_exec(int use_waitpid)
 441 {
 442         int pid, pidfd = 0;
 443         int status, ret;
 444         pthread_t t1;
 445         time_t prog_start = time(NULL);
 446         const char *test_name = "pidfd_poll check for premature notification on child thread exec";
 447
 448         ksft_print_msg("Parent: pid: %d\n", getpid());
 449         pid = pidfd_clone(CLONE_PIDFD, &pidfd, child_poll_exec_test);
 450         if (pid < 0)
 451                 ksft_exit_fail_msg("%s test: pidfd_clone failed (ret %d, errno %d)\n",
 452                                    test_name, pid, errno);
 453
 454         ksft_print_msg("Parent: Waiting for Child (%d) to complete.\n", pid);
 455
 456         if (use_waitpid) {
 457                 ret = waitpid(pid, &status, 0);
 458                 if (ret == -1)
 459                         ksft_print_msg("Parent: error\n");
 460
 461                 if (ret == pid)
 462                         ksft_print_msg("Parent: Child process waited for.\n");
 463         } else {
 464                 poll_pidfd(test_name, pidfd);
 465         }
 466
 467         time_t prog_time = time(NULL) - prog_start;
 468
 469         ksft_print_msg("Time waited for child: %lu\n", prog_time);
 470
 471         close(pidfd);
 472
 473         if (prog_time < CHILD_THREAD_MIN_WAIT || prog_time > CHILD_THREAD_MIN_WAIT + 2)
 474                 ksft_exit_fail_msg("%s test: Failed\n", test_name);
 475         else
 476                 ksft_test_result_pass("%s test: Passed\n", test_name);
 477 }
 478
 479 static void *test_pidfd_poll_leader_exit_thread(void *priv)
 480 {
 481         ksft_print_msg("Child Thread: starting. pid %d tid %d ; and sleeping\n",
 482                         getpid(), syscall(SYS_gettid));
 483         sleep(CHILD_THREAD_MIN_WAIT);
 484         ksft_print_msg("Child Thread: DONE. pid %d tid %d\n", getpid(), syscall(SYS_gettid));
 485         return NULL;
 486 }
 487
 488 static time_t *child_exit_secs;
 489 static int child_poll_leader_exit_test(void *args)
 490 {
 491         pthread_t t1, t2;
 492
 493         ksft_print_msg("Child: starting. pid %d tid %d\n", getpid(), syscall(SYS_gettid));
 494         pthread_create(&t1, NULL, test_pidfd_poll_leader_exit_thread, NULL);
 495         pthread_create(&t2, NULL, test_pidfd_poll_leader_exit_thread, NULL);
 496
 497         /*
 498          * glibc exit calls exit_group syscall, so explicity call exit only
 499          * so that only the group leader exits, leaving the threads alone.
 500          */
 501         *child_exit_secs = time(NULL);
 502         syscall(SYS_exit, 0);
 503 }
 504
 505 static void test_pidfd_poll_leader_exit(int use_waitpid)
 506 {
 507         int pid, pidfd = 0;
 508         int status, ret;
 509         time_t prog_start = time(NULL);
 510         const char *test_name = "pidfd_poll check for premature notification on non-empty"
 511                                 "group leader exit";
 512
 513         child_exit_secs = mmap(NULL, sizeof *child_exit_secs, PROT_READ | PROT_WRITE,
 514                         MAP_SHARED | MAP_ANONYMOUS, -1, 0);
 515
 516         if (child_exit_secs == MAP_FAILED)
 517                 ksft_exit_fail_msg("%s test: mmap failed (errno %d)\n",
 518                                    test_name, errno);
 519
 520         ksft_print_msg("Parent: pid: %d\n", getpid());
 521         pid = pidfd_clone(CLONE_PIDFD, &pidfd, child_poll_leader_exit_test);
 522         if (pid < 0)
 523                 ksft_exit_fail_msg("%s test: pidfd_clone failed (ret %d, errno %d)\n",
 524                                    test_name, pid, errno);
 525
 526         ksft_print_msg("Parent: Waiting for Child (%d) to complete.\n", pid);
 527
 528         if (use_waitpid) {
 529                 ret = waitpid(pid, &status, 0);
 530                 if (ret == -1)
 531                         ksft_print_msg("Parent: error\n");
 532         } else {
 533                 /*
 534                  * This sleep tests for the case where if the child exits, and is in
 535                  * EXIT_ZOMBIE, but the thread group leader is non-empty, then the poll
 536                  * doesn't prematurely return even though there are active threads
 537                  */
 538                 sleep(1);
 539                 poll_pidfd(test_name, pidfd);
 540         }
 541
 542         if (ret == pid)
 543                 ksft_print_msg("Parent: Child process waited for.\n");
 544
 545         time_t since_child_exit = time(NULL) - *child_exit_secs;
 546
 547         ksft_print_msg("Time since child exit: %lu\n", since_child_exit);
 548
 549         close(pidfd);
 550
 551         if (since_child_exit < CHILD_THREAD_MIN_WAIT ||
 552                         since_child_exit > CHILD_THREAD_MIN_WAIT + 2)
 553                 ksft_exit_fail_msg("%s test: Failed\n", test_name);
 554         else
 555                 ksft_test_result_pass("%s test: Passed\n", test_name);
 556 }
 557
 558 int main(int argc, char **argv)
 559 {
 560         ksft_print_header();
 561         ksft_set_plan(8);
 562
 563         test_pidfd_poll_exec(0);
 564         test_pidfd_poll_exec(1);
 565         test_pidfd_poll_leader_exit(0);
 566         test_pidfd_poll_leader_exit(1);
 567         test_pidfd_send_signal_syscall_support();
 568         test_pidfd_send_signal_simple_success();
 569         test_pidfd_send_signal_exited_fail();
 570         test_pidfd_send_signal_recycled_pid_fail();
 571
 572         return ksft_exit_pass();
 573 }