GNU C Library master sources branch master updated. glibc-2.24-518-gb0a679f

[carlos at sourceware dot org]

This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".

The branch, master has been updated
       via  b0a679f4fd5363809a972b697e8a0b1fc66fcbb1 (commit)
      from  57707b7fcc38855869321f8c7827bfe21d729f37 (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=b0a679f4fd5363809a972b697e8a0b1fc66fcbb1

commit b0a679f4fd5363809a972b697e8a0b1fc66fcbb1
Author: Carlos O'Donell <carlos@redhat.com>
Date:   Fri Dec 23 13:39:23 2016 -0500

    Add deferred cancellation regression test for getpwuid_r.
    
    The fix in commit 312be3f9f5eab1643d7dcc7728c76d413d4f2640 resolved
    several cancellation issues in several APIs.  This regression test is
    designed to double check that at least getpwuid_r remainds correctly
    implemented and does not provide additional unintended cancellation
    points that may leave locks in an inconsistent state.

diff --git a/ChangeLog b/ChangeLog
index 8c6ebd2..48ea5d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2016-12-24  Carlos O'Donell  <carlos@redhat.com>
 
+	* nss/Makefile [ifeq (yes,$(have-thread-library))]
+	(tests): Add tst-cancel-getpwuid_r.
+	* nss/tst-cancel-getpwuid_r.c: New file.
+
 	[BZ #11941]
 	* elf/dl-close.c (_dl_close): Take dl_load_lock to examine map.
 	Remove assert (map->l_init_called); if DF_1_NODELETE is set.
diff --git a/nss/Makefile b/nss/Makefile
index 1f016d9..9132e17 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -54,6 +54,12 @@ tests			= test-netdb tst-nss-test1 test-digits-dots \
 			  $(tests-static)
 xtests			= bug-erange
 
+# If we have a thread library then we can test cancellation against
+# some routines like getpwuid_r.
+ifeq (yes,$(have-thread-library))
+tests += tst-cancel-getpwuid_r
+endif
+
 # Specify rules for the nss_* modules.  We have some services.
 services		:= files db
 
@@ -125,3 +131,7 @@ $(objpfx)/libnss_test1.so$(libnss_test1.so-version): $(objpfx)/libnss_test1.so
 	$(make-link)
 endif
 $(objpfx)tst-nss-test1.out: $(objpfx)/libnss_test1.so$(libnss_test1.so-version)
+
+ifeq (yes,$(have-thread-library))
+$(objpfx)tst-cancel-getpwuid_r: $(shared-thread-library)
+endif
diff --git a/nss/tst-cancel-getpwuid_r.c b/nss/tst-cancel-getpwuid_r.c
new file mode 100644
index 0000000..aeb959d
--- /dev/null
+++ b/nss/tst-cancel-getpwuid_r.c
@@ -0,0 +1,180 @@
+/* Test cancellation of getpwuid_r.
+   Copyright (C) 2016 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
+   <http://www.gnu.org/licenses/>.  */
+
+/* Test if cancellation of getpwuid_r incorrectly leaves internal
+   function state locked resulting in hang of subsequent calls to
+   getpwuid_r.  The main thread creates a second thread which will do
+   the calls to getpwuid_r.  A semaphore is used by the second thread to
+   signal to the main thread that it is as close as it can be to the
+   call site of getpwuid_r.  The goal of the semaphore is to avoid any
+   cancellable function calls between the sem_post and the call to
+   getpwuid_r.  The main thread then attempts to cancel the second
+   thread.  Without the fixes the cancellation happens at any number of
+   calls to cancellable functions in getpuid_r, but with the fix the
+   cancellation either does not happen or happens only at expected
+   points where the internal state is consistent.  We use an explicit
+   pthread_testcancel call to terminate the loop in a timely fashion
+   if the implementation does not have a cancellation point.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <pwd.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <semaphore.h>
+#include <errno.h>
+#include <support/support.h>
+
+sem_t started;
+char *wbuf;
+long wbufsz;
+
+void
+worker_free (void *arg)
+{
+  free (arg);
+}
+
+static void *
+worker (void *arg)
+{
+  int ret;
+  unsigned int iter = 0;
+  struct passwd pwbuf, *pw;
+  uid_t uid;
+
+  uid = geteuid ();
+
+  /* Use a reasonable sized buffer.  Note that _SC_GETPW_R_SIZE_MAX is
+     just a hint and not any kind of maximum value.  */
+  wbufsz = sysconf (_SC_GETPW_R_SIZE_MAX);
+  if (wbufsz == -1)
+    wbufsz = 1024;
+  wbuf = xmalloc (wbufsz);
+
+  pthread_cleanup_push (worker_free, wbuf);
+  sem_post (&started);
+  while (1)
+    {
+      iter++;
+
+      ret = getpwuid_r (uid, &pwbuf, wbuf, wbufsz, &pw);
+
+      /* The call to getpwuid_r may not cancel so we need to test
+	 for cancellation after some number of iterations of the
+	 function.  Choose an arbitrary 100,000 iterations of running
+	 getpwuid_r in a tight cancellation loop before testing for
+	 cancellation.  */
+      if (iter > 100000)
+	pthread_testcancel ();
+
+      if (ret == ERANGE)
+	{
+	  /* Increase the buffer size.  */
+	  free (wbuf);
+	  wbufsz = wbufsz * 2;
+	  wbuf = xmalloc (wbufsz);
+	}
+
+    }
+  pthread_cleanup_pop (1);
+
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  int ret;
+  char *buf;
+  long bufsz;
+  void *retval;
+  struct passwd pwbuf, *pw;
+  pthread_t thread;
+
+  /* Configure the test to only use files. We control the files plugin
+     as part of glibc so we assert that it should be deferred
+     cancellation safe.  */
+  __nss_configure_lookup ("passwd", "files");
+
+  /* Use a reasonable sized buffer.  Note that  _SC_GETPW_R_SIZE_MAX is
+     just a hint and not any kind of maximum value.  */
+  bufsz = sysconf (_SC_GETPW_R_SIZE_MAX);
+  if (bufsz == -1)
+    bufsz = 1024;
+  buf = xmalloc (bufsz);
+
+  sem_init (&started, 0, 0);
+
+  pthread_create (&thread, NULL, worker, NULL);
+
+  do
+  {
+    ret = sem_wait (&started);
+    if (ret == -1 && errno != EINTR)
+      {
+        printf ("FAIL: Failed to wait for second thread to start.\n");
+	exit (EXIT_FAILURE);
+      }
+  }
+  while (ret != 0);
+
+  printf ("INFO: Cancelling thread\n");
+  if ((ret = pthread_cancel (thread)) != 0)
+    {
+      printf ("FAIL: Failed to cancel thread. Returned %d\n", ret);
+      exit (EXIT_FAILURE);
+    }
+
+  printf ("INFO: Joining...\n");
+  pthread_join (thread, &retval);
+  if (retval != PTHREAD_CANCELED)
+    {
+      printf ("FAIL: Thread was not cancelled.\n");
+      exit (EXIT_FAILURE);
+    }
+  printf ("INFO: Joined, trying getpwuid_r call\n");
+
+  /* Before the fix in 312be3f9f5eab1643d7dcc7728c76d413d4f2640 for this
+     issue the cancellation point could happen in any number of internal
+     calls, and therefore locks would be left held and the following
+     call to getpwuid_r would block and the test would time out.  */
+  do
+    {
+      ret = getpwuid_r (geteuid (), &pwbuf, buf, bufsz, &pw);
+      if (ret == ERANGE)
+	{
+	  /* Increase the buffer size.  */
+	  free (buf);
+	  bufsz = bufsz * 2;
+	  buf = xmalloc (bufsz);
+	}
+    }
+  while (ret == ERANGE);
+
+  free (buf);
+
+  /* Before the fix we would never get here.  */
+  printf ("PASS: Canceled getpwuid_r successfully"
+	  " and called it again without blocking.\n");
+
+  return 0;
+}
+
+#include <support/test-driver.c>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                   |    4 +
 nss/Makefile                |   10 +++
 nss/tst-cancel-getpwuid_r.c |  180 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 194 insertions(+), 0 deletions(-)
 create mode 100644 nss/tst-cancel-getpwuid_r.c


hooks/post-receive
-- 
GNU C Library master sources