[v6] elf: Add tst-ldconfig-bad-aux-cache test [BZ #18093]

diff --git a/elf/Makefile b/elf/Makefile
index 4895489208..08e2f999bf 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -156,6 +156,9 @@  tests-static-internal := tst-tls1-static tst-tls2-static \
 CRT-tst-tls1-static-non-pie := $(csu-objpfx)crt1.o
 tst-tls1-static-non-pie-no-pie = yes
 
+tests-container = \
+			  tst-ldconfig-bad-aux-cache
+
 tests := tst-tls9 tst-leaks1 \
 	tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
 	tst-auxv
diff --git a/elf/tst-ldconfig-bad-aux-cache.c b/elf/tst-ldconfig-bad-aux-cache.c
new file mode 100644
index 0000000000..68ce90a956
--- /dev/null
+++ b/elf/tst-ldconfig-bad-aux-cache.c
@@ -0,0 +1,117 @@ 
+/* Test ldconfig does not segfault when aux-cache is corrupted (Bug 18093).
+   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 does the following:
+   Run ldconfig to create the caches.
+   Corrupt the caches.
+   Run ldconfig again.
+   At each step we verify that ldconfig does not crash.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <ftw.h>
+#include <stdint.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xunistd.h>
+
+#include <dirent.h>
+
+static int
+display_info (const char *fpath, const struct stat *sb,
+              int tflag, struct FTW *ftwbuf)
+{
+  printf ("info: %-3s %2d %7jd   %-40s %d %s\n",
+          (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" :
+          (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" :
+          (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" :
+          (tflag == FTW_SLN) ? "sln" : "???",
+          ftwbuf->level, (intmax_t) sb->st_size,
+          fpath, ftwbuf->base, fpath + ftwbuf->base);
+  /* To tell nftw to continue.  */
+  return 0;
+}
+
+/* Run ldconfig with a corrupt aux-cache, in particular we test for size
+   truncation that might happen if a previous ldconfig run failed or if
+   there were storage or power issues while we were writing the file.
+   We want ldconfig not to crash, and it should be able to do so by
+   computing the expected size of the file (bug 18093).  */
+static int
+do_test (void)
+{
+  char *prog = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+  char *const args[] = { prog, NULL };
+  const char *path = "/var/cache/ldconfig/aux-cache";
+  struct stat64 fs;
+  long int size, new_size, i;
+  int status;
+  pid_t pid;
+
+  /* Create the needed directories. */
+  xmkdirp ("/var/cache/ldconfig", 0777);
+
+  pid = xfork ();
+  /* Run ldconfig fist to generate the aux-cache.  */
+  if (pid == 0)
+    {
+      execv (args[0], args);
+      _exit (1);
+    }
+  else
+    {
+      xwaitpid (pid, &status, 0);
+      TEST_COMPARE(status, 0);
+      xstat (path, &fs);
+
+      size = fs.st_size;
+      /* Run 3 tests, each truncating aux-cache shorter and shorter.  */
+      for (i = 3; i > 0; i--)
+        {
+          new_size = size * i / 4;
+          if (truncate (path, new_size))
+              FAIL_EXIT1 ("truncation failed: %m");
+          if (nftw (path, display_info, 1000, 0) == -1)
+              FAIL_EXIT1 ("nftw failed.");
+
+          pid = xfork ();
+          /* Verify that ldconfig can run with a truncated
+             aux-cache and doesn't crash.  */
+          if (pid == 0)
+            {
+              execv (args[0], args);
+              _exit (1);
+            }
+          else
+            {
+              xwaitpid (pid, &status, 0);
+              TEST_COMPARE(status, 0);
+            }
+        }
+    }
+
+  free (prog);
+  return 0;
+}
+
+#include <support/test-driver.c>