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

   1 /* Basic tests for Linux pidfd interfaces.
   2    Copyright (C) 2022 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 <support/capture_subprocess.h>
  22 #include <support/check.h>
  23 #include <support/process_state.h>
  24 #include <support/support.h>
  25 #include <support/xsignal.h>
  26 #include <support/xunistd.h>
  27 #include <support/xsocket.h>
  28 #include <sys/pidfd.h>
  29 #include <sys/wait.h>
  30
  31 #define REMOTE_PATH "/dev/null"
  32
  33 /* The pair of sockets used for coordination.  The subprocess uses
  34    sockets[1].  */
  35 static int sockets[2];
  36
  37 static pid_t ppid;
  38 static uid_t puid;
  39
  40 static void
  41 sighandler (int sig)
  42 {
  43 }
  44
  45 static void
  46 subprocess (void)
  47 {
  48   xsignal (SIGUSR1, sighandler);
  49   xsignal (SIGUSR2, sighandler);
  50
  51   /* Check first pidfd_send_signal with default NULL siginfo_t argument.  */
  52   {
  53     sigset_t set;
  54     sigemptyset (&set);
  55     sigaddset (&set, SIGUSR1);
  56     siginfo_t info;
  57     TEST_COMPARE (sigtimedwait (&set, &info, NULL), SIGUSR1);
  58     TEST_COMPARE (info.si_signo, SIGUSR1);
  59     TEST_COMPARE (info.si_errno, 0);
  60     TEST_COMPARE (info.si_code, SI_USER);
  61     TEST_COMPARE (info.si_pid, ppid);
  62     TEST_COMPARE (info.si_uid, puid);
  63   }
  64
  65   /* Check second pidfd_send_signal with crafted siginfo_t argument.  */
  66   {
  67     sigset_t set;
  68     sigemptyset (&set);
  69     sigaddset (&set, SIGUSR2);
  70     siginfo_t info;
  71     TEST_COMPARE (sigtimedwait (&set, &info, NULL), SIGUSR2);
  72     TEST_COMPARE (info.si_signo, SIGUSR2);
  73     TEST_COMPARE (info.si_errno, EAGAIN);
  74     TEST_COMPARE (info.si_code, -10);
  75     TEST_COMPARE (info.si_pid, ppid);
  76     TEST_COMPARE (info.si_uid, puid);
  77   }
  78
  79   /* Send a local file descriptor value to check pidfd_getfd.  */
  80   int remote_fd = xopen (REMOTE_PATH, O_WRONLY | O_CLOEXEC, 0);
  81   xsendto (sockets[1], &remote_fd, sizeof (remote_fd), 0, NULL, 0);
  82
  83   /* Wait for final pidfd_send_signal.  */
  84   pause ();
  85
  86   _exit (0);
  87 }
  88
  89 static int
  90 do_test (void)
  91 {
  92   {
  93     /* The pidfd_getfd syscall was the last in the set of pidfd related
  94        syscalls added to the kernel.  Use pidfd_getfd to decide if this
  95        kernel has pidfd support that we can test.  */
  96     int r = pidfd_getfd (0, 0, 1);
  97     TEST_VERIFY_EXIT (r == -1);
  98     if (errno == ENOSYS)
  99       FAIL_UNSUPPORTED ("kernel does not support pidfd_getfd, skipping test");
 100   }
 101
 102   ppid = getpid ();
 103   puid = getuid ();
 104
 105   TEST_COMPARE (socketpair (AF_UNIX, SOCK_STREAM, 0, sockets), 0);
 106
 107   pid_t pid = xfork ();
 108   if (pid == 0)
 109     {
 110       xclose (sockets[0]);
 111       subprocess ();
 112     }
 113   xclose (sockets[1]);
 114
 115   TEST_COMPARE (pidfd_open (-1, 0), -1);
 116   TEST_COMPARE (errno, EINVAL);
 117
 118   int pidfd = pidfd_open (pid, 0);
 119   TEST_VERIFY (pidfd != -1);
 120
 121   /* Wait for first sigtimedwait.  */
 122   support_process_state_wait (pid, support_process_state_sleeping);
 123   TEST_COMPARE (pidfd_send_signal (pidfd, SIGUSR1, NULL, 0), 0);
 124
 125   /* Wait for second sigtimedwait.  */
 126   support_process_state_wait (pid, support_process_state_sleeping);
 127   {
 128     siginfo_t info =
 129       {
 130         .si_signo = SIGUSR2,
 131         .si_errno = EAGAIN,
 132         .si_code = -10,
 133         .si_pid = ppid,
 134         .si_uid = puid
 135       };
 136     TEST_COMPARE (pidfd_send_signal (pidfd, SIGUSR2, &info, 0), 0);
 137   }
 138
 139   /* Get remote file descriptor to check for pidfd_getfd.  */
 140   {
 141     int remote_fd;
 142     xrecvfrom (sockets[0], &remote_fd, sizeof (remote_fd), 0, NULL, 0);
 143
 144     int fd = pidfd_getfd (pidfd, remote_fd, 0);
 145     /* pidfd_getfd may fail with EPERM if the process does not have
 146        PTRACE_MODE_ATTACH_REALCREDS permissions. This means the call
 147        may be denied if the process doesn't have CAP_SYS_PTRACE or
 148        if a LSM security_ptrace_access_check denies access.  */
 149     if (fd == -1 && errno == EPERM)
 150       {
 151         TEST_COMPARE (pidfd_send_signal (pidfd, SIGKILL, NULL, 0), 0);
 152         FAIL_UNSUPPORTED ("don't have permission to use pidfd_getfd on pidfd, "
 153                           "skipping test");
 154       }
 155     TEST_VERIFY (fd > 0);
 156
 157     char *path = xasprintf ("/proc/%d/fd/%d", pid, remote_fd);
 158     char *resolved = xreadlink (path);
 159     TEST_COMPARE_STRING (resolved, REMOTE_PATH);
 160
 161     int remote_fd_mode = fcntl (fd, F_GETFL);
 162     TEST_VERIFY (remote_fd_mode != -1);
 163     TEST_VERIFY (remote_fd_mode & O_WRONLY);
 164
 165     int remote_fd_flags = fcntl (fd, F_GETFD);
 166     TEST_VERIFY (remote_fd_flags != -1);
 167     TEST_VERIFY (remote_fd_flags & FD_CLOEXEC);
 168   }
 169
 170   TEST_COMPARE (pidfd_send_signal (pidfd, SIGKILL, NULL, 0), 0);
 171   {
 172     siginfo_t info;
 173     int r = waitid (P_PIDFD, pidfd, &info, WEXITED);
 174     TEST_COMPARE (r, 0);
 175     TEST_COMPARE (info.si_status, SIGKILL);
 176     TEST_COMPARE (info.si_code, CLD_KILLED);
 177   }
 178
 179   return 0;
 180 }
 181
 182 #include <support/test-driver.c>