sysdeps/unix/sysv/linux/tst-pidfd.c

   1 /* Basic tests for Linux pidfd interfaces.
   2    Copyright (C) 2022-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <limits.h>
  22 #include <support/capture_subprocess.h>
  23 #include <support/check.h>
  24 #include <support/process_state.h>
  25 #include <support/support.h>
  26 #include <support/xsignal.h>
  27 #include <support/xunistd.h>
  28 #include <support/xsocket.h>
  29 #include <sys/pidfd.h>
  30 #include <sys/wait.h>
  31 #include <stdlib.h>
  32 #include <unistd.h>
  33
  34 #define REMOTE_PATH "/dev/null"
  35
  36 /* The pair of sockets used for coordination.  The subprocess uses
  37    sockets[1].  */
  38 static int sockets[2];
  39
  40 static pid_t ppid;
  41 static uid_t puid;
  42
  43 static void
  44 sighandler (int sig)
  45 {
  46 }
  47
  48 static void
  49 subprocess (void)
  50 {
  51   xsignal (SIGUSR1, sighandler);
  52   xsignal (SIGUSR2, sighandler);
  53
  54   /* Check first pidfd_send_signal with default NULL siginfo_t argument.  */
  55   {
  56     sigset_t set;
  57     sigemptyset (&set);
  58     sigaddset (&set, SIGUSR1);
  59     siginfo_t info;
  60     TEST_COMPARE (sigtimedwait (&set, &info, NULL), SIGUSR1);
  61     TEST_COMPARE (info.si_signo, SIGUSR1);
  62     TEST_COMPARE (info.si_errno, 0);
  63     TEST_COMPARE (info.si_code, SI_USER);
  64     TEST_COMPARE (info.si_pid, ppid);
  65     TEST_COMPARE (info.si_uid, puid);
  66   }
  67
  68   /* Check second pidfd_send_signal with crafted siginfo_t argument.  */
  69   {
  70     sigset_t set;
  71     sigemptyset (&set);
  72     sigaddset (&set, SIGUSR2);
  73     siginfo_t info;
  74     TEST_COMPARE (sigtimedwait (&set, &info, NULL), SIGUSR2);
  75     TEST_COMPARE (info.si_signo, SIGUSR2);
  76     TEST_COMPARE (info.si_errno, EAGAIN);
  77     TEST_COMPARE (info.si_code, -10);
  78     TEST_COMPARE (info.si_pid, ppid);
  79     TEST_COMPARE (info.si_uid, puid);
  80   }
  81
  82   /* Send a local file descriptor value to check pidfd_getfd.  */
  83   int remote_fd = xopen (REMOTE_PATH, O_WRONLY | O_CLOEXEC, 0);
  84   xsendto (sockets[1], &remote_fd, sizeof (remote_fd), 0, NULL, 0);
  85
  86   /* Wait for final pidfd_send_signal.  */
  87   pause ();
  88
  89   _exit (0);
  90 }
  91
  92 static int
  93 do_test (void)
  94 {
  95   {
  96     /* The pidfd_getfd syscall was the last in the set of pidfd related
  97        syscalls added to the kernel.  Use pidfd_getfd to decide if this
  98        kernel has pidfd support that we can test.  */
  99     int r = pidfd_getfd (0, 0, 1);
 100     TEST_VERIFY_EXIT (r == -1);
 101     if (errno == ENOSYS)
 102       FAIL_UNSUPPORTED ("kernel does not support pidfd_getfd, skipping test");
 103   }
 104
 105   ppid = getpid ();
 106   puid = getuid ();
 107
 108   /* Sanity check for invalid inputs.  */
 109   TEST_COMPARE (pidfd_getpid (-1), -1);
 110   TEST_COMPARE (errno, EBADF);
 111
 112   {
 113     pid_t pid = pidfd_getpid (STDOUT_FILENO);
 114     TEST_COMPARE (pid, -1);
 115     TEST_COMPARE (errno, EBADF);
 116   }
 117
 118   /* Check if pidfd_getpid returns ESRCH for exited subprocess.  */
 119   {
 120     pid_t pidfork = xfork ();
 121     if (pidfork == 0)
 122       _exit (EXIT_SUCCESS);
 123     int pidfork_pidfd = pidfd_open (pidfork, 0);
 124
 125     /* The process might be still running or already in zombie state, in
 126        either case the PID is still allocated to the process.  */
 127     pid_t pid = pidfd_getpid (pidfork_pidfd);
 128     TEST_COMPARE (pidfork, pid);
 129     if (pid > 0)
 130       support_process_state_wait (pid, support_process_state_zombie);
 131
 132     siginfo_t info;
 133     TEST_COMPARE (waitid (P_PIDFD, pidfork_pidfd, &info, WEXITED), 0);
 134     TEST_COMPARE (info.si_pid, pidfork);
 135     TEST_COMPARE (info.si_status, 0);
 136     TEST_COMPARE (info.si_code, CLD_EXITED);
 137
 138     /* Once the process is reaped the associated PID is not available.  */
 139     pid = pidfd_getpid (pidfork_pidfd);
 140     TEST_COMPARE (pid, -1);
 141     TEST_COMPARE (errno, ESRCH);
 142
 143     xclose (pidfork_pidfd);
 144   }
 145
 146   TEST_COMPARE (socketpair (AF_UNIX, SOCK_STREAM, 0, sockets), 0);
 147
 148   pid_t pid = xfork ();
 149   if (pid == 0)
 150     {
 151       xclose (sockets[0]);
 152       subprocess ();
 153     }
 154   xclose (sockets[1]);
 155
 156   TEST_COMPARE (pidfd_open (-1, 0), -1);
 157   TEST_COMPARE (errno, EINVAL);
 158
 159   int pidfd = pidfd_open (pid, 0);
 160   TEST_VERIFY (pidfd != -1);
 161
 162   TEST_COMPARE (pidfd_getpid (INT_MAX), -1);
 163   {
 164     pid_t querypid = pidfd_getpid (pidfd);
 165     TEST_COMPARE (querypid, pid);
 166   }
 167
 168   /* Wait for first sigtimedwait.  */
 169   support_process_state_wait (pid, support_process_state_sleeping);
 170   TEST_COMPARE (pidfd_send_signal (pidfd, SIGUSR1, NULL, 0), 0);
 171
 172   /* Wait for second sigtimedwait.  */
 173   support_process_state_wait (pid, support_process_state_sleeping);
 174   {
 175     siginfo_t info =
 176       {
 177         .si_signo = SIGUSR2,
 178         .si_errno = EAGAIN,
 179         .si_code = -10,
 180         .si_pid = ppid,
 181         .si_uid = puid
 182       };
 183     TEST_COMPARE (pidfd_send_signal (pidfd, SIGUSR2, &info, 0), 0);
 184   }
 185
 186   /* Get remote file descriptor to check for pidfd_getfd.  */
 187   {
 188     int remote_fd;
 189     xrecvfrom (sockets[0], &remote_fd, sizeof (remote_fd), 0, NULL, 0);
 190
 191     int fd = pidfd_getfd (pidfd, remote_fd, 0);
 192     /* pidfd_getfd may fail with EPERM if the process does not have
 193        PTRACE_MODE_ATTACH_REALCREDS permissions. This means the call
 194        may be denied if the process doesn't have CAP_SYS_PTRACE or
 195        if a LSM security_ptrace_access_check denies access.  */
 196     if (fd == -1 && errno == EPERM)
 197       {
 198         TEST_COMPARE (pidfd_send_signal (pidfd, SIGKILL, NULL, 0), 0);
 199         FAIL_UNSUPPORTED ("don't have permission to use pidfd_getfd on pidfd, "
 200                           "skipping test");
 201       }
 202     TEST_VERIFY (fd > 0);
 203
 204     char *path = xasprintf ("/proc/%d/fd/%d", pid, remote_fd);
 205     char *resolved = xreadlink (path);
 206     TEST_COMPARE_STRING (resolved, REMOTE_PATH);
 207
 208     int remote_fd_mode = fcntl (fd, F_GETFL);
 209     TEST_VERIFY (remote_fd_mode != -1);
 210     TEST_VERIFY (remote_fd_mode & O_WRONLY);
 211
 212     int remote_fd_flags = fcntl (fd, F_GETFD);
 213     TEST_VERIFY (remote_fd_flags != -1);
 214     TEST_VERIFY (remote_fd_flags & FD_CLOEXEC);
 215   }
 216
 217   TEST_COMPARE (pidfd_send_signal (pidfd, SIGKILL, NULL, 0), 0);
 218   {
 219     siginfo_t info;
 220     int r = waitid (P_PIDFD, pidfd, &info, WEXITED);
 221     TEST_COMPARE (r, 0);
 222     TEST_COMPARE (info.si_status, SIGKILL);
 223     TEST_COMPARE (info.si_code, CLD_KILLED);
 224   }
 225
 226   return 0;
 227 }
 228
 229 #include <support/test-driver.c>