diff options
Diffstat (limited to 'login/tst-pututxline-cache.c')
| -rw-r--r-- | login/tst-pututxline-cache.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/login/tst-pututxline-cache.c b/login/tst-pututxline-cache.c new file mode 100644 index 0000000000..3f30dd1776 --- /dev/null +++ b/login/tst-pututxline-cache.c @@ -0,0 +1,193 @@ +/* Test case for cache invalidation after concurrent write (bug 24882). + Copyright (C) 2019 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 <http://www.gnu.org/licenses/>. */ + +/* This test writes an entry to the utmpx file, reads it (so that it + is cached) in process1, and overwrites the same entry in process2 + with something that does not match the search criteria. At this + point, the cache of the first process is stale, and when process1 + attempts to write a new record which would have gone to the same + place (as indicated by the cache), it needs to realize that it has + to pick a different slot because the old slot is now used for + something else. */ + +#include <errno.h> +#include <stdlib.h> +#include <string.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 <utmp.h> +#include <utmpx.h> + +/* Set to the path of the utmp file. */ +static char *utmp_file; + +/* Used to synchronize the subprocesses. The barrier itself is + allocated in shared memory. */ +static pthread_barrier_t *barrier; + +/* setutxent with error checking. */ +static void +xsetutxent (void) +{ + errno = 0; + setutxent (); + TEST_COMPARE (errno, 0); +} + +/* getutxent with error checking. */ +static struct utmpx * +xgetutxent (void) +{ + errno = 0; + struct utmpx *result = getutxent (); + if (result == NULL) + FAIL_EXIT1 ("getutxent: %m"); + return result; +} + +static void +put_entry (const char *id, pid_t pid, const char *user, const char *line) +{ + struct utmpx ut = + { + .ut_type = LOGIN_PROCESS, + .ut_pid = pid, + .ut_host = "localhost", + }; + strcpy (ut.ut_id, id); + strncpy (ut.ut_user, user, sizeof (ut.ut_user)); + strncpy (ut.ut_line, line, sizeof (ut.ut_line)); + TEST_VERIFY (pututxline (&ut) != NULL); +} + +/* Use two cooperating subprocesses to avoid issues related to + unlock-on-close semantics of POSIX advisory locks. */ + +static __attribute__ ((noreturn)) void +process1 (void) +{ + TEST_COMPARE (utmpname (utmp_file), 0); + + /* Create an entry. */ + xsetutxent (); + put_entry ("1", 101, "root", "process1"); + + /* Retrieve the entry. This will fill the internal cache. */ + { + errno = 0; + setutxent (); + TEST_COMPARE (errno, 0); + struct utmpx ut = + { + .ut_type = LOGIN_PROCESS, + .ut_line = "process1", + }; + struct utmpx *result = getutxline (&ut); + if (result == NULL) + FAIL_EXIT1 ("getutxline (\"process1\"): %m"); + TEST_COMPARE (result->ut_pid, 101); + } + + /* Signal the other process to overwrite the entry. */ + xpthread_barrier_wait (barrier); + + /* Wait for the other process to complete the write operation. */ + xpthread_barrier_wait (barrier); + + /* Add another entry. Note: This time, there is no setutxent call. */ + put_entry ("1", 103, "root", "process1"); + + _exit (0); +} + +static void +process2 (void *closure) +{ + /* Wait for the first process to write its entry. */ + xpthread_barrier_wait (barrier); + + /* Truncate the file. The glibc interface does not support + re-purposing records, but an external expiration mechanism may + trigger this. */ + TEST_COMPARE (truncate64 (utmp_file, 0), 0); + + /* Write the replacement entry. */ + TEST_COMPARE (utmpname (utmp_file), 0); + xsetutxent (); + put_entry ("2", 102, "user", "process2"); + + /* Signal the other process that the entry has been replaced. */ + xpthread_barrier_wait (barrier); +} + +static int +do_test (void) +{ + xclose (create_temp_file ("tst-tumpx-cache-write-", &utmp_file)); + { + 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); + } + + /* Run both subprocesses in parallel. */ + { + pid_t pid1 = xfork (); + if (pid1 == 0) + process1 (); + support_isolate_in_subprocess (process2, NULL); + int status; + xwaitpid (pid1, &status, 0); + TEST_COMPARE (status, 0); + } + + /* Check that the utmpx database contains the expected records. */ + { + TEST_COMPARE (utmpname (utmp_file), 0); + xsetutxent (); + + struct utmpx *ut = xgetutxent (); + TEST_COMPARE_STRING (ut->ut_id, "2"); + TEST_COMPARE (ut->ut_pid, 102); + TEST_COMPARE_STRING (ut->ut_user, "user"); + TEST_COMPARE_STRING (ut->ut_line, "process2"); + + ut = xgetutxent (); + TEST_COMPARE_STRING (ut->ut_id, "1"); + TEST_COMPARE (ut->ut_pid, 103); + TEST_COMPARE_STRING (ut->ut_user, "root"); + TEST_COMPARE_STRING (ut->ut_line, "process1"); + + if (getutxent () != NULL) + FAIL_EXIT1 ("additional utmpx entry"); + } + + xpthread_barrier_destroy (barrier); + support_shared_free (barrier); + free (utmp_file); + + return 0; +} + +#include <support/test-driver.c> |