debug: Add regression tests for BZ 30932

Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

2 files changed, 84 insertions, 0 deletions

diff --git a/debug/Makefile b/debug/Makefile
index 434e52f..c49e5d8 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -178,6 +178,7 @@ CFLAGS-tst-longjmp_chk3.c += -fexceptions -fasynchronous-unwind-tables
 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
 
 # _FORTIFY_SOURCE tests.
 # Auto-generate tests for _FORTIFY_SOURCE for different levels, compilers and
@@ -284,6 +285,7 @@ tests = \
   tst-longjmp_chk \
   tst-longjmp_chk2 \
   tst-realpath-chk \
+  tst-sprintf-fortify-rdonly \
   tst-sprintf-fortify-unchecked \
   # tests
 
diff --git a/debug/tst-sprintf-fortify-rdonly.c b/debug/tst-sprintf-fortify-rdonly.c
new file mode 100644
index 0000000..78dece9
--- /dev/null
+++ b/debug/tst-sprintf-fortify-rdonly.c
@@ -0,0 +1,82 @@
+/* Testcase for BZ 30932.
+   Copyright (C) 2023 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <setjmp.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+
+jmp_buf chk_fail_buf;
+bool chk_fail_ok;
+
+const char *str2 = "F";
+char buf2[10] = "%s";
+
+static int
+do_test (void)
+{
+  struct rlimit rl;
+  int max_fd = 24;
+
+  if (getrlimit (RLIMIT_NOFILE, &rl) == -1)
+    FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m");
+
+  max_fd = (rl.rlim_cur < max_fd ? rl.rlim_cur : max_fd);
+  rl.rlim_cur = max_fd;
+
+  if (setrlimit (RLIMIT_NOFILE, &rl) == 1)
+    FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m");
+
+  /* Exhaust the file descriptor limit with temporary files.  */
+  int nfiles = 0;
+  for (; nfiles < max_fd; nfiles++)
+    {
+      int fd = create_temp_file ("tst-sprintf-fortify-rdonly-.", NULL);
+      if (fd == -1)
+	{
+	  if (errno != EMFILE)
+	    FAIL_EXIT1 ("create_temp_file: %m");
+	  break;
+	}
+    }
+  TEST_VERIFY_EXIT (nfiles != 0);
+
+  /* When the format string is writable and contains %n,
+     with -D_FORTIFY_SOURCE=2 it causes __chk_fail.  However, if libc can not
+     open procfs to check if the input format string in within a writable
+     memory segment, the fortify version can not perform the check.  */
+  char buf[128];
+  int n1;
+  int n2;
+
+  strcpy (buf2 + 2, "%n%s%n");
+  if (sprintf (buf, buf2, str2, &n1, str2, &n2) != 2
+      || n1 != 1 || n2 != 2)
+    FAIL_EXIT1 ("sprintf failed: %s %d %d", buf, n1, n2);
+
+  return 0;
+}
+
+#include <support/test-driver.c>