debug: Add fortify syslog tests

It requires to be in a container tests to avoid logging bogus
information on the system.  The syslog also requires to be checked in
a different process because the internal printf call will abort with
the internal syslog lock taken (which makes subsequent syslog calls
deadlock).

Checked on aarch64, armhf, x86_64, and i686.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

debug/Makefile

@@ -179,6 +179,7 @@ CPPFLAGS-tst-longjmp_chk3.c += $(no-fortify-source),-D_FORTIFY_SOURCE=1
 CPPFLAGS-tst-realpath-chk.c += $(no-fortify-source),-D_FORTIFY_SOURCE=2
 CPPFLAGS-tst-chk-cancel.c += $(no-fortify-source),-D_FORTIFY_SOURCE=2
 CFLAGS-tst-sprintf-fortify-rdonly.c += $(no-fortify-source),-D_FORTIFY_SOURCE=2
+CFLAGS-tst-fortify-syslog.c += $(no-fortify-source),-D_FORTIFY_SOURCE=2
 
 # _FORTIFY_SOURCE tests.
 # Auto-generate tests for _FORTIFY_SOURCE for different levels, compilers and
@@ -293,6 +294,10 @@ tests-time64 += \
   $(tests-all-time64-chk) \
   # tests-time64
 
+tests-container += \
+  tst-fortify-syslog \
+  # tests-container
+
 ifeq ($(have-ssp),yes)
 tests += tst-ssp-1
 endif

debug/tst-fortify-syslog.c

@@ -0,0 +1,128 @@
+/* Fortify tests for syslog interface.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
+   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 <stdarg.h>
+#include <setjmp.h>
+#include <syslog.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/capture_subprocess.h>
+
+static const char *str2 = "F";
+static char buf2[10] = "%s";
+
+static volatile int chk_fail_ok;
+static jmp_buf chk_fail_buf;
+
+static void
+handler (int sig)
+{
+  if (chk_fail_ok)
+    {
+      chk_fail_ok = 0;
+      longjmp (chk_fail_buf, 1);
+    }
+  else
+    _exit (127);
+}
+
+#define FAIL()						\
+  do {							\
+      printf ("Failure on line %d\n", __LINE__);	\
+      support_record_failure ();			\
+  } while (0)
+#define CHK_FAIL_START					\
+  chk_fail_ok = 1;					\
+  if (! setjmp (chk_fail_buf))				\
+    {
+#define CHK_FAIL_END					\
+      chk_fail_ok = 0;					\
+      FAIL ();						\
+    }
+
+static void
+call_vsyslog (int priority, const char *format, ...)
+{
+  va_list va;
+  va_start (va, format);
+  vsyslog (priority, format, va);
+  va_end (va);
+}
+
+static void
+run_syslog_chk (void *closure)
+{
+  int n1;
+  CHK_FAIL_START
+  syslog (LOG_USER | LOG_DEBUG, buf2, str2, &n1, str2, &n1);
+  CHK_FAIL_END
+}
+
+static void
+run_vsyslog_chk (void *closure)
+{
+  int n1;
+  CHK_FAIL_START
+  call_vsyslog (LOG_USER | LOG_DEBUG, buf2, str2, &n1, str2, &n1);
+  CHK_FAIL_END
+}
+
+static int
+do_test (void)
+{
+  set_fortify_handler (handler);
+
+  int n1, n2;
+
+  n1 = n2 = 0;
+  syslog (LOG_USER | LOG_DEBUG, "%s%n%s%n", str2, &n1, str2, &n2);
+  TEST_COMPARE (n1, 1);
+  TEST_COMPARE (n2, 2);
+
+  n1 = n2 = 0;
+  call_vsyslog (LOG_USER | LOG_DEBUG, "%s%n%s%n", str2, &n1, str2, &n2);
+  TEST_COMPARE (n1, 1);
+  TEST_COMPARE (n2, 2);
+
+  strcpy (buf2 + 2, "%n%s%n");
+
+  /* The wrapper tests need to be in a subprocess because the abort called by
+     printf does not unlock the internal syslog lock.  */
+  {
+    struct support_capture_subprocess result
+      = support_capture_subprocess (run_syslog_chk, NULL);
+    support_capture_subprocess_check (&result, "syslog", 0, sc_allow_stderr);
+    support_capture_subprocess_free (&result);
+  }
+
+  {
+    struct support_capture_subprocess result
+      = support_capture_subprocess (run_vsyslog_chk, NULL);
+    support_capture_subprocess_check (&result, "syslog", 0, sc_allow_stderr);
+    support_capture_subprocess_free (&result);
+  }
+
+  return 0;
+}
+
+#include <support/test-driver.c>