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/* Test the lock upgrade path in tst-pututxline.
Copyright (C) 2019-2024 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; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
/* pututxline upgrades the read lock on the file to a write lock.
This test verifies that if the lock upgrade fails, the utmp
subsystem remains in a consistent state, so that pututxline can be
called again. */
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <support/check.h>
#include <support/namespace.h>
#include <support/support.h>
#include <support/temp_file.h>
#include <support/xthread.h>
#include <support/xunistd.h>
#include <unistd.h>
#include <utmp.h>
#include <utmpx.h>
/* Path to the temporary utmp file. */
static char *path;
/* Used to synchronize the subprocesses. The barrier itself is
allocated in shared memory. */
static pthread_barrier_t *barrier;
/* Use pututxline to write an entry for PID. */
static struct utmpx *
write_entry (pid_t pid)
{
struct utmpx ut =
{
.ut_type = LOGIN_PROCESS,
.ut_id = "1",
.ut_user = "root",
.ut_pid = pid,
.ut_line = "entry",
.ut_host = "localhost",
};
return pututxline (&ut);
}
/* Create the initial entry in a subprocess, so that the utmp
subsystem in the original process is not disturbed. */
static void
subprocess_create_entry (void *closure)
{
TEST_COMPARE (utmpname (path), 0);
TEST_VERIFY (write_entry (101) != NULL);
}
/* Acquire an advisory read lock on PATH. */
__attribute__ ((noreturn)) static void
subprocess_lock_file (void)
{
int fd = xopen (path, O_RDONLY, 0);
struct flock64 fl =
{
.l_type = F_RDLCK,
fl.l_whence = SEEK_SET,
};
TEST_COMPARE (fcntl64 (fd, F_SETLKW, &fl), 0);
/* Signal to the main process that the lock has been acquired. */
xpthread_barrier_wait (barrier);
/* Wait for the unlock request from the main process. */
xpthread_barrier_wait (barrier);
/* Implicitly unlock the file. */
xclose (fd);
/* Overwrite the existing entry. */
TEST_COMPARE (utmpname (path), 0);
errno = 0;
setutxent ();
TEST_COMPARE (errno, 0);
TEST_VERIFY (write_entry (102) != NULL);
errno = 0;
endutxent ();
TEST_COMPARE (errno, 0);
_exit (0);
}
static int
do_test (void)
{
xclose (create_temp_file ("tst-pututxline-lockfail-", &path));
{
pthread_barrierattr_t attr;
xpthread_barrierattr_init (&attr);
xpthread_barrierattr_setpshared (&attr, PTHREAD_SCOPE_PROCESS);
barrier = support_shared_allocate (sizeof (*barrier));
xpthread_barrier_init (barrier, &attr, 2);
xpthread_barrierattr_destroy (&attr);
}
/* Write the initial entry. */
support_isolate_in_subprocess (subprocess_create_entry, NULL);
pid_t locker_pid = xfork ();
if (locker_pid == 0)
subprocess_lock_file ();
/* Wait for the file locking to complete. */
xpthread_barrier_wait (barrier);
/* Try to add another entry. This attempt will fail, with EINTR or
EAGAIN. */
TEST_COMPARE (utmpname (path), 0);
TEST_VERIFY (write_entry (102) == NULL);
if (errno != EINTR)
TEST_COMPARE (errno, EAGAIN);
/* Signal the subprocess to overwrite the entry. */
xpthread_barrier_wait (barrier);
/* Wait for write and unlock to complete. */
{
int status;
xwaitpid (locker_pid, &status, 0);
TEST_COMPARE (status, 0);
}
/* The file is no longer locked, so this operation will succeed. */
TEST_VERIFY (write_entry (103) != NULL);
errno = 0;
endutxent ();
TEST_COMPARE (errno, 0);
/* Check that there is just one entry with the expected contents.
If pututxline becomes desynchronized internally, the entry is not
overwritten (bug 24902). */
errno = 0;
setutxent ();
TEST_COMPARE (errno, 0);
struct utmpx *ut = getutxent ();
TEST_VERIFY_EXIT (ut != NULL);
TEST_COMPARE (ut->ut_type, LOGIN_PROCESS);
TEST_COMPARE_STRING (ut->ut_id, "1");
TEST_COMPARE_STRING (ut->ut_user, "root");
TEST_COMPARE (ut->ut_pid, 103);
TEST_COMPARE_STRING (ut->ut_line, "entry");
TEST_COMPARE_STRING (ut->ut_host, "localhost");
TEST_VERIFY (getutxent () == NULL);
errno = 0;
endutxent ();
TEST_COMPARE (errno, 0);
xpthread_barrier_destroy (barrier);
support_shared_free (barrier);
free (path);
return 0;
}
#include <support/test-driver.c>
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