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e7190fc73d
This interface allows to obtain the associated process ID from the
process file descriptor. It is done by parsing the procps fdinfo
information. Its prototype is:
pid_t pidfd_getpid (int fd)
It returns the associated pid or -1 in case of an error and sets the
errno accordingly. The possible errno values are those from open, read,
and close (used on procps parsing), along with:
- EBADF if the FD is negative, does not have a PID associated, or if
the fdinfo fields contain a value larger than pid_t.
- EREMOTE if the PID is in a separate namespace.
- ESRCH if the process is already terminated.
Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PIDFD or waitid
support), Linux 5.4 (full support), and Linux 6.2.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
124 lines
3.7 KiB
C
124 lines
3.7 KiB
C
/* Specific tests for Linux pidfd_getpid.
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Copyright (C) 2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <sched.h>
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#include <stdlib.h>
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#include <support/check.h>
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#include <support/xunistd.h>
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#include <support/test-driver.h>
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#include <sys/pidfd.h>
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#include <sys/wait.h>
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#include <sys/mount.h>
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static int
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do_test (void)
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{
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{
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/* The pidfd_getfd syscall was the last in the set of pidfd related
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syscalls added to the kernel. Use pidfd_getfd to decide if this
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kernel has pidfd support that we can test. */
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int r = pidfd_getfd (0, 0, 1);
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TEST_VERIFY_EXIT (r == -1);
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if (errno == ENOSYS)
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FAIL_UNSUPPORTED ("kernel does not support pidfd_getfd, skipping test");
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if (errno == EPERM)
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FAIL_UNSUPPORTED ("kernel does not allow pidfd_getfd, skipping test");
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}
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/* Check if pidfd_getpid returns EREMOTE for process not in current
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namespace. */
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{
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pid_t child0 = xfork ();
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TEST_VERIFY_EXIT (child0 >= 0);
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if (child0 == 0)
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{
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/* Create another unrelated descriptor, so child2 will inherit the
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file descriptor. */
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pid_t child1 = xfork ();
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TEST_VERIFY_EXIT (child1 >= 0);
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if (child1 == 0)
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_exit (0);
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int child1_pidfd = pidfd_open (child1, 0);
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TEST_VERIFY_EXIT (child1_pidfd != -1);
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if (unshare (CLONE_NEWNS | CLONE_NEWUSER | CLONE_NEWPID) < 0)
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{
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/* Older kernels may not support all the options, or security
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policy may block this call. */
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if (errno == EINVAL || errno == EPERM || errno == ENOSPC)
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exit (EXIT_UNSUPPORTED);
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FAIL_EXIT1 ("unshare user/fs/pid failed: %m");
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}
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if (mount (NULL, "/", NULL, MS_REC | MS_PRIVATE, 0) != 0)
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{
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/* This happens if we're trying to create a nested container,
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like if the build is running under podman, and we lack
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priviledges. */
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if (errno == EPERM)
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_exit (EXIT_UNSUPPORTED);
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else
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_exit (EXIT_FAILURE);
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}
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pid_t child2 = xfork ();
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if (child2 > 0)
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{
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int status;
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xwaitpid (child2, &status, 0);
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TEST_VERIFY (WIFEXITED (status));
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xwaitpid (child1, &status, 0);
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TEST_VERIFY (WIFEXITED (status));
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_exit (WEXITSTATUS (status));
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}
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/* Now that we're pid 1 (effectively "root") we can mount /proc */
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if (mount ("proc", "/proc", "proc", 0, NULL) != 0)
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{
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if (errno == EPERM)
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_exit (EXIT_UNSUPPORTED);
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else
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_exit (EXIT_FAILURE);
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}
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TEST_COMPARE (pidfd_getpid (child1_pidfd), -1);
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TEST_COMPARE (errno, EREMOTE);
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_exit (EXIT_SUCCESS);
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}
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int child0_pidfd = pidfd_open (child0, 0);
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TEST_VERIFY_EXIT (child0_pidfd != -1);
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pid_t child0pid = pidfd_getpid (child0_pidfd);
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siginfo_t info;
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TEST_COMPARE (waitid (P_PIDFD, child0_pidfd, &info, WEXITED), 0);
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if (info.si_status == EXIT_UNSUPPORTED)
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FAIL_UNSUPPORTED ("unable to unshare user/fs/pid");
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TEST_COMPARE (info.si_status, 0);
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TEST_COMPARE (info.si_code, CLD_EXITED);
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TEST_COMPARE (info.si_pid, child0pid);
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}
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return 0;
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}
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#include <support/test-driver.c>
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