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/* Test cancellation of getpwuid_r.
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Copyright (C) 2016-2018 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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<http://www.gnu.org/licenses/>. */
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/* Test if cancellation of getpwuid_r incorrectly leaves internal
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function state locked resulting in hang of subsequent calls to
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getpwuid_r. The main thread creates a second thread which will do
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the calls to getpwuid_r. A semaphore is used by the second thread to
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signal to the main thread that it is as close as it can be to the
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call site of getpwuid_r. The goal of the semaphore is to avoid any
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cancellable function calls between the sem_post and the call to
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getpwuid_r. The main thread then attempts to cancel the second
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thread. Without the fixes the cancellation happens at any number of
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calls to cancellable functions in getpuid_r, but with the fix the
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cancellation either does not happen or happens only at expected
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points where the internal state is consistent. We use an explicit
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pthread_testcancel call to terminate the loop in a timely fashion
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if the implementation does not have a cancellation point. */
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#include <stdio.h>
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#include <stdlib.h>
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#include <pthread.h>
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#include <pwd.h>
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#include <nss.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <semaphore.h>
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#include <errno.h>
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#include <support/support.h>
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sem_t started;
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char *wbuf;
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long wbufsz;
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void
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worker_free (void *arg)
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{
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free (arg);
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}
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static void *
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worker (void *arg)
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{
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int ret;
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unsigned int iter = 0;
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struct passwd pwbuf, *pw;
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uid_t uid;
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uid = geteuid ();
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/* Use a reasonable sized buffer. Note that _SC_GETPW_R_SIZE_MAX is
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just a hint and not any kind of maximum value. */
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wbufsz = sysconf (_SC_GETPW_R_SIZE_MAX);
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if (wbufsz == -1)
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wbufsz = 1024;
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wbuf = xmalloc (wbufsz);
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pthread_cleanup_push (worker_free, wbuf);
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sem_post (&started);
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while (1)
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{
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iter++;
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ret = getpwuid_r (uid, &pwbuf, wbuf, wbufsz, &pw;;
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/* The call to getpwuid_r may not cancel so we need to test
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for cancellation after some number of iterations of the
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function. Choose an arbitrary 100,000 iterations of running
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getpwuid_r in a tight cancellation loop before testing for
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cancellation. */
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if (iter > 100000)
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pthread_testcancel ();
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if (ret == ERANGE)
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{
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/* Increase the buffer size. */
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free (wbuf);
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wbufsz = wbufsz * 2;
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wbuf = xmalloc (wbufsz);
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}
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}
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pthread_cleanup_pop (1);
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return NULL;
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}
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static int
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do_test (void)
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{
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int ret;
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char *buf;
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long bufsz;
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void *retval;
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struct passwd pwbuf, *pw;
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pthread_t thread;
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/* Configure the test to only use files. We control the files plugin
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as part of glibc so we assert that it should be deferred
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cancellation safe. */
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__nss_configure_lookup ("passwd", "files");
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/* Use a reasonable sized buffer. Note that _SC_GETPW_R_SIZE_MAX is
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just a hint and not any kind of maximum value. */
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bufsz = sysconf (_SC_GETPW_R_SIZE_MAX);
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if (bufsz == -1)
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bufsz = 1024;
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buf = xmalloc (bufsz);
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sem_init (&started, 0, 0);
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pthread_create (&thread, NULL, worker, NULL);
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do
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{
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ret = sem_wait (&started);
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if (ret == -1 && errno != EINTR)
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{
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printf ("FAIL: Failed to wait for second thread to start.\n");
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exit (EXIT_FAILURE);
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}
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}
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while (ret != 0);
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printf ("INFO: Cancelling thread\n");
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if ((ret = pthread_cancel (thread)) != 0)
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{
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printf ("FAIL: Failed to cancel thread. Returned %d\n", ret);
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exit (EXIT_FAILURE);
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}
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printf ("INFO: Joining...\n");
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pthread_join (thread, &retval);
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if (retval != PTHREAD_CANCELED)
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{
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printf ("FAIL: Thread was not cancelled.\n");
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exit (EXIT_FAILURE);
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}
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printf ("INFO: Joined, trying getpwuid_r call\n");
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/* Before the fix in 312be3f9f5eab1643d7dcc7728c76d413d4f2640 for this
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issue the cancellation point could happen in any number of internal
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calls, and therefore locks would be left held and the following
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call to getpwuid_r would block and the test would time out. */
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do
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{
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ret = getpwuid_r (geteuid (), &pwbuf, buf, bufsz, &pw;;
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if (ret == ERANGE)
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{
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/* Increase the buffer size. */
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free (buf);
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bufsz = bufsz * 2;
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buf = xmalloc (bufsz);
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}
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}
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while (ret == ERANGE);
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free (buf);
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/* Before the fix we would never get here. */
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printf ("PASS: Canceled getpwuid_r successfully"
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" and called it again without blocking.\n");
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return 0;
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}
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#define TIMEOUT 900
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#include <support/test-driver.c>
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