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glibc/posix/tst-spawn.c
Adhemerval Zanella Netto 0d6f9f6265 posix: Add pidfd_spawn and pidfd_spawnp (BZ 30349) 
Returning a pidfd allows a process to keep a race-free handle for a
child process, otherwise, the caller will need to either use pidfd_open
(which still might be subject to TOCTOU) or keep the old racy interface
base on pid_t.

To correct use pifd_spawn, the kernel must support not only returning
the pidfd with clone/clone3 but also waitid (P_PIDFD) (added on Linux
5.4).  If kernel does not support the waitid, pidfd return ENOSYS.
It avoids the need to racy workarounds, such as reading the procfs
fdinfo to get the pid to use along with other wait interfaces.

These interfaces are similar to the posix_spawn and posix_spawnp, with
the only difference being it returns a process file descriptor (int)
instead of a process ID (pid_t).  Their prototypes are:

  int pidfd_spawn (int *restrict pidfd,
                   const char *restrict file,
                   const posix_spawn_file_actions_t *restrict facts,
                   const posix_spawnattr_t *restrict attrp,
                   char *const argv[restrict],
                   char *const envp[restrict])

  int pidfd_spawnp (int *restrict pidfd,
                    const char *restrict path,
                    const posix_spawn_file_actions_t *restrict facts,
                    const posix_spawnattr_t *restrict attrp,
                    char *const argv[restrict_arr],
                    char *const envp[restrict_arr]);

A new symbol is used instead of a posix_spawn extension to avoid
possible issues with language bindings that might track the return
argument lifetime.  Although on Linux pid_t and int are interchangeable,
POSIX only states that pid_t should be a signed integer.

Both symbols reuse the posix_spawn posix_spawn_file_actions_t and
posix_spawnattr_t, to void rehash posix_spawn API or add a new one. It
also means that both interfaces support the same attribute and file
actions, and a new flag or file action on posix_spawn is also added
automatically for pidfd_spawn.

Also, using posix_spawn plumbing allows the reusing of most of the
current testing with some changes:

  - waitid is used instead of waitpid since it is a more generic
    interface.

  - tst-posix_spawn-setsid.c is adapted to take into consideration that
    the caller can check for session id directly.  The test now spawns
itself and writes the session id as a file instead.

  - tst-spawn3.c need to know where pidfd_spawn is used so it keeps an
    extra file description unused.

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>
2023-09-05 13:08:59 -03:00

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/* Tests for spawn.
Copyright (C) 2000-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <getopt.h>
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <spawn.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <support/check.h>
#include <support/xunistd.h>
#include <support/temp_file.h>
#include <support/support.h>
#include <tst-spawn.h>
/* Nonzero if the program gets called via `exec'. */
static int restart;
#define CMDLINE_OPTIONS \
{ "restart", no_argument, &restart, 1 },
/* Name of the temporary files. */
static char *name1;
static char *name2;
static char *name3;
static char *name5;
/* Descriptors for the temporary files. */
static int temp_fd1 = -1;
static int temp_fd2 = -1;
static int temp_fd3 = -1;
static int temp_fd5 = -1;
/* The contents of our files. */
static const char fd1string[] = "This file should get closed";
static const char fd2string[] = "This file should stay opened";
static const char fd3string[] = "This file will be opened";
static const char fd5string[] = "This file should stay opened (O_CLOEXEC)";
/* We have a preparation function. */
static void
do_prepare (int argc, char *argv[])
{
/* We must not open any files in the restart case. */
if (restart)
return;
TEST_VERIFY_EXIT ((temp_fd1 = create_temp_file ("spawn", &name1)) != -1);
TEST_VERIFY_EXIT ((temp_fd2 = create_temp_file ("spawn", &name2)) != -1);
TEST_VERIFY_EXIT ((temp_fd3 = create_temp_file ("spawn", &name3)) != -1);
TEST_VERIFY_EXIT ((temp_fd5 = create_temp_file ("spawn", &name5)) != -1);
int flags;
TEST_VERIFY_EXIT ((flags = fcntl (temp_fd5, F_GETFD, &flags)) != -1);
TEST_COMPARE (fcntl (temp_fd5, F_SETFD, flags | FD_CLOEXEC), 0);
}
#define PREPARE do_prepare
static int
handle_restart (const char *fd1s, const char *fd2s, const char *fd3s,
const char *fd4s, const char *name, const char *fd5s)
{
char buf[100];
int fd1;
int fd2;
int fd3;
int fd4;
int fd5;
/* First get the descriptors. */
fd1 = atol (fd1s);
fd2 = atol (fd2s);
fd3 = atol (fd3s);
fd4 = atol (fd4s);
fd5 = atol (fd5s);
/* Sanity check. */
TEST_VERIFY_EXIT (fd1 != fd2);
TEST_VERIFY_EXIT (fd1 != fd3);
TEST_VERIFY_EXIT (fd1 != fd4);
TEST_VERIFY_EXIT (fd2 != fd3);
TEST_VERIFY_EXIT (fd2 != fd4);
TEST_VERIFY_EXIT (fd3 != fd4);
TEST_VERIFY_EXIT (fd4 != fd5);
/* First the easy part: read from the file descriptor which is
supposed to be open. */
TEST_COMPARE (xlseek (fd2, 0, SEEK_CUR), strlen (fd2string));
/* The duped descriptor must have the same position. */
TEST_COMPARE (xlseek (fd4, 0, SEEK_CUR), strlen (fd2string));
TEST_COMPARE (xlseek (fd2, 0, SEEK_SET), 0);
TEST_COMPARE (xlseek (fd4, 0, SEEK_CUR), 0);
TEST_COMPARE (read (fd2, buf, sizeof buf), strlen (fd2string));
TEST_COMPARE_BLOB (fd2string, strlen (fd2string), buf, strlen (fd2string));
/* Now read from the third file. */
TEST_COMPARE (read (fd3, buf, sizeof buf), strlen (fd3string));
TEST_COMPARE_BLOB (fd3string, strlen (fd3string), buf, strlen (fd3string));
/* Try to write to the file. This should not be allowed. */
TEST_COMPARE (write (fd3, "boo!", 4), -1);
TEST_COMPARE (errno, EBADF);
/* Now try to read the first file. First make sure it is not opened. */
TEST_COMPARE (lseek (fd1, 0, SEEK_CUR), (off_t) -1);
TEST_COMPARE (errno, EBADF);
/* Now open the file and read it. */
fd1 = xopen (name, O_RDONLY, 0600);
TEST_COMPARE (read (fd1, buf, sizeof buf), strlen (fd1string));
TEST_COMPARE_BLOB (fd1string, strlen (fd1string), buf, strlen (fd1string));
TEST_COMPARE (xlseek (fd5, 0, SEEK_SET), 0);
TEST_COMPARE (read (fd5, buf, sizeof buf), strlen (fd5string));
TEST_COMPARE_BLOB (fd5string, strlen (fd5string), buf, strlen (fd5string));
return 0;
}
static int
do_test (int argc, char *argv[])
{
PID_T_TYPE pid;
int fd4;
siginfo_t sinfo;
posix_spawn_file_actions_t actions;
char fd1name[18];
char fd2name[18];
char fd3name[18];
char fd4name[18];
char fd5name[18];
char *name3_copy;
char *spargv[13];
int i;
/* We must have
- one or four parameters left if called initially
+ path for ld.so optional
+ "--library-path" optional
+ the library path optional
+ the application name
- six parameters left if called through re-execution
+ file descriptor number which is supposed to be closed
+ the open file descriptor
+ the newly opened file descriptor
+ the duped second descriptor
+ the name of the closed descriptor
+ the duped fourth file descriptor which O_CLOEXEC should be
remove by adddup2.
*/
if (argc != (restart ? 7 : 2) && argc != (restart ? 7 : 5))
FAIL_EXIT1 ("wrong number of arguments (%d)", argc);
if (restart)
return handle_restart (argv[1], argv[2], argv[3], argv[4], argv[5],
argv[6]);
/* Prepare the test. We are creating four files: two which file descriptor
will be marked with FD_CLOEXEC, another which is not. */
/* Write something in the files. */
xwrite (temp_fd1, fd1string, strlen (fd1string));
xwrite (temp_fd2, fd2string, strlen (fd2string));
xwrite (temp_fd3, fd3string, strlen (fd3string));
xwrite (temp_fd5, fd5string, strlen (fd5string));
/* Close the third file. It'll be opened by `spawn'. */
xclose (temp_fd3);
/* Tell `spawn' what to do. */
TEST_COMPARE (posix_spawn_file_actions_init (&actions), 0);
/* Close `temp_fd1'. */
TEST_COMPARE (posix_spawn_file_actions_addclose (&actions, temp_fd1), 0);
/* We want to open the third file. */
name3_copy = xstrdup (name3);
TEST_COMPARE (posix_spawn_file_actions_addopen (&actions, temp_fd3,
name3_copy,
O_RDONLY, 0666),
0);
/* Overwrite the name to check that a copy has been made. */
memset (name3_copy, 'X', strlen (name3_copy));
/* We dup the second descriptor. */
fd4 = MAX (2, MAX (temp_fd1, MAX (temp_fd2, MAX (temp_fd3, temp_fd5)))) + 1;
TEST_COMPARE (posix_spawn_file_actions_adddup2 (&actions, temp_fd2, fd4),
0);
/* We clear the O_CLOEXEC on fourth descriptor, so it should be
stay open on child. */
TEST_COMPARE (posix_spawn_file_actions_adddup2 (&actions, temp_fd5,
temp_fd5),
0);
/* Now spawn the process. */
snprintf (fd1name, sizeof fd1name, "%d", temp_fd1);
snprintf (fd2name, sizeof fd2name, "%d", temp_fd2);
snprintf (fd3name, sizeof fd3name, "%d", temp_fd3);
snprintf (fd4name, sizeof fd4name, "%d", fd4);
snprintf (fd5name, sizeof fd5name, "%d", temp_fd5);
for (i = 0; i < (argc == (restart ? 7 : 5) ? 4 : 1); i++)
spargv[i] = argv[i + 1];
spargv[i++] = (char *) "--direct";
spargv[i++] = (char *) "--restart";
spargv[i++] = fd1name;
spargv[i++] = fd2name;
spargv[i++] = fd3name;
spargv[i++] = fd4name;
spargv[i++] = name1;
spargv[i++] = fd5name;
spargv[i] = NULL;
TEST_COMPARE (POSIX_SPAWN (&pid, argv[1], &actions, NULL, spargv, environ),
0);
/* Wait for the children. */
TEST_COMPARE (WAITID (P_PID, pid, &sinfo, WEXITED), 0);
TEST_COMPARE (sinfo.si_code, CLD_EXITED);
TEST_COMPARE (sinfo.si_status, 0);
/* Same test but with a NULL pid argument. */
TEST_COMPARE (POSIX_SPAWN (NULL, argv[1], &actions, NULL, spargv, environ),
0);
/* Cleanup. */
TEST_COMPARE (posix_spawn_file_actions_destroy (&actions), 0);
free (name3_copy);
/* Wait for the children. */
TEST_COMPARE (WAITID (P_ALL, 0, &sinfo, WEXITED), 0);
TEST_COMPARE (sinfo.si_code, CLD_EXITED);
TEST_COMPARE (sinfo.si_status, 0);
return 0;
}
#define TEST_FUNCTION_ARGV do_test
#include <support/test-driver.c>
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