BZ #17702: Fix recursive dlopen.

diff --git a/dlfcn/Makefile b/dlfcn/Makefile
index 1fad0a5..537fe85 100644
--- a/dlfcn/Makefile
+++ b/dlfcn/Makefile
@@ -36,13 +36,13 @@  endif
 ifeq (yes,$(build-shared))
 tests = glrefmain failtest tst-dladdr default errmsg1 tstcxaatexit \
 	bug-dlopen1 bug-dlsym1 tst-dlinfo bug-atexit1 bug-atexit2 \
-	bug-atexit3 tstatexit bug-dl-leaf
+	bug-atexit3 tstatexit bug-dl-leaf tst-rec-dlopen
 endif
 modules-names = glreflib1 glreflib2 glreflib3 failtestmod defaultmod1 \
 		defaultmod2 errmsg1mod modatexit modcxaatexit \
 		bug-dlsym1-lib1 bug-dlsym1-lib2 bug-atexit1-lib \
 		bug-atexit2-lib bug-atexit3-lib bug-dl-leaf-lib \
-		bug-dl-leaf-lib-cb
+		bug-dl-leaf-lib-cb moddummy1 moddummy2
 
 failtestmod.so-no-z-defs = yes
 glreflib2.so-no-z-defs = yes
@@ -139,3 +139,6 @@  $(objpfx)bug-dl-leaf: $(objpfx)bug-dl-leaf-lib.so
 $(objpfx)bug-dl-leaf.out: $(objpfx)bug-dl-leaf-lib-cb.so
 $(objpfx)bug-dl-leaf-lib.so: $(libdl)
 $(objpfx)bug-dl-leaf-lib-cb.so: $(objpfx)bug-dl-leaf-lib.so
+
+$(objpfx)tst-rec-dlopen: $(libdl)
+$(objpfx)tst-rec-dlopen.out: $(objpfx)moddummy1.so $(objpfx)moddummy2.so
diff --git a/dlfcn/moddummy1.c b/dlfcn/moddummy1.c
new file mode 100644
index 0000000..6e549fa
--- /dev/null
+++ b/dlfcn/moddummy1.c
@@ -0,0 +1,10 @@ 
+/* Provide a dummy DSO for tst-rec-dlopen to use.  */
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+dummy1 (void)
+{
+  printf ("Called dummy1()\n");
+  return 1;
+}
diff --git a/dlfcn/moddummy2.c b/dlfcn/moddummy2.c
new file mode 100644
index 0000000..cb4edc8
--- /dev/null
+++ b/dlfcn/moddummy2.c
@@ -0,0 +1,13 @@ 
+/* Provide a dummy DSO for tst-rec-dlopen to use.  */
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+dummy2 (void)
+{
+  printf ("Called dummy2()\n");
+  /* If the outer dlopen is not dummy1 (becuase of some error)
+     then tst-rec-dlopen will see a value of -1 as the returned
+     result and fail.  */
+  return -1;
+}
diff --git a/dlfcn/tst-rec-dlopen.c b/dlfcn/tst-rec-dlopen.c
new file mode 100644
index 0000000..35b08d4
--- /dev/null
+++ b/dlfcn/tst-rec-dlopen.c
@@ -0,0 +1,144 @@ 
+/* Test recursive dlopen using malloc hooks.
+   Copyright (C) 1998-2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+   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/>.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <dlfcn.h>
+
+#define DSO "moddummy1.so"
+#define FUNC "dummy1"
+
+#define DSO1 "moddummy2.so"
+#define FUNC1 "dummy2"
+
+/* Result of the called function.  */
+int func_result;
+
+/* Prototype for my hook.  */
+void *custom_malloc_hook (size_t, const void *);
+
+/* Pointer to old malloc hooks.  */
+void *(*old_malloc_hook) (size_t, const void *);
+
+/* Call function func_name in DSO dso_name via dlopen.  */
+void
+call_func (const char *dso_name, const char *func_name)
+{
+  int ret;
+  void *dso;
+  int (*func) (void);
+  char *err;
+
+  /* Open the DSO.  */
+  dso = dlopen (dso_name, RTLD_NOW|RTLD_GLOBAL);
+  if (dso == NULL)
+    {
+      err = dlerror ();
+      fprintf (stderr, "%s\n", err);
+      exit (1);
+    }
+  /* Clear any errors.  */
+  dlerror ();
+
+  /* Lookup func.  */
+  *(void **) (&func) = dlsym (dso, func_name);
+  if (func == NULL)
+    {
+      err = dlerror ();
+      if (err != NULL)
+        {
+	  fprintf (stderr, "%s\n", err);
+	  exit (1);
+        }
+    }
+  /* Call func.  */
+  func_result = (*func) ();
+
+  /* Close the library and look for errors too.  */
+  ret = dlclose (dso);
+  if (ret != 0)
+    {
+      err = dlerror ();
+      fprintf (stderr, "%s\n", err);
+      exit (1);
+    }
+
+}
+
+/* Empty hook that does nothing.  */
+void *
+custom_malloc_hook (size_t size, const void *caller)
+{
+  void *result;
+  /* Restore old hooks.  */
+  __malloc_hook = old_malloc_hook;
+  /* First call a function in another library via dlopen.  */
+  call_func (DSO1, FUNC1);
+  /* Called recursively.  */
+  result = malloc (size);
+  /* Restore new hooks.  */
+  __malloc_hook = custom_malloc_hook;
+  return result;
+}
+
+static int
+do_test (void)
+{
+  /* Save old hook.  */
+  old_malloc_hook = __malloc_hook;
+  /* Install new hook.  */
+  __malloc_hook = custom_malloc_hook;
+
+  /* Bug 17702 fixes two things:
+       * A recursive dlopen unmapping the ld.so.cache.
+       * An assertion that _r_debug is RT_CONSISTENT at entry to dlopen.
+     We can only test the latter. Testing the former requires modifying
+     ld.so.conf to cache the dummy libraries, then running ldconfig,
+     then run the test. If you do all of that (and glibc's test
+     infrastructure doesn't support that yet) then the test will
+     SEGFAULT without the fix. If you don't do that, then the test
+     will abort because of the assert described in detail below.  */
+  call_func (DSO, FUNC);
+
+  /* Restore old hook.  */
+  __malloc_hook = old_malloc_hook;
+
+  /* The function dummy2() is called by the malloc hook. Check to
+     see that it was called. This ensures the second recursive
+     dlopen happened and we called the function in that library.
+     Before the fix you either get a SIGSEGV when accessing mmap'd
+     ld.so.cache data or an assertion failure about _r_debug not
+     beint RT_CONSISTENT.  We don't test for the SIGSEGV since it
+     would require finding moddummy1 or moddummy2 in the cache and
+     we don't have any infrastructure to test that, but the _r_debug
+     assertion triggers.  */
+  printf ("Returned result is %d\n", func_result);
+  if (func_result <= 0)
+    {
+      printf ("FAIL: Function call_func() not called.\n");
+      exit (1);
+    }
+
+  printf ("PASS: Function call_func() called more than once.\n");
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 91fef95..396b541 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -174,9 +174,12 @@  _dl_cache_libcmp (const char *p1, const char *p2)
 
 /* Look up NAME in ld.so.cache and return the file name stored there, or null
    if none is found.  The cache is loaded if it was not already.  If loading
-   the cache previously failed there will be no more attempts to load it.  */
-
-const char *
+   the cache previously failed there will be no more attempts to load it.
+   The caller is responsible for freeing the returned string.  The ld.so.cache
+   may be unmapped at any time by a completing recursive dlopen and
+   this function must take care that it does not return references to
+   any data in the mapping.  */
+char *
 internal_function
 _dl_load_cache_lookup (const char *name)
 {
@@ -289,7 +292,17 @@  _dl_load_cache_lookup (const char *name)
       && best != NULL)
     _dl_debug_printf ("  trying file=%s\n", best);
 
-  return best;
+  if (best == NULL)
+    return NULL;
+
+  /* The double copy is *required* since malloc may be interposed
+     and call dlopen itself whose completion would unmap the data
+     we are accessing. Therefore we must make the copy of the
+     mapping data without using malloc.  */
+  char *temp;
+  temp = alloca (strlen (best) + 1);
+  strcpy (temp, best);
+  return strdup (temp);
 }
 
 #ifndef MAP_COPY
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 7a03ccf..02285f3 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -2051,7 +2051,7 @@  _dl_map_object (struct link_map *loader, const char *name,
 	{
 	  /* Check the list of libraries in the file /etc/ld.so.cache,
 	     for compatibility with Linux's ldconfig program.  */
-	  const char *cached = _dl_load_cache_lookup (name);
+	  char *cached = _dl_load_cache_lookup (name);
 
 	  if (cached != NULL)
 	    {
@@ -2075,6 +2075,7 @@  _dl_map_object (struct link_map *loader, const char *name,
 		      if (memcmp (cached, dirp, system_dirs_len[cnt]) == 0)
 			{
 			  /* The prefix matches.  Don't use the entry.  */
+			  free (cached);
 			  cached = NULL;
 			  break;
 			}
@@ -2092,14 +2093,9 @@  _dl_map_object (struct link_map *loader, const char *name,
 				    LA_SER_CONFIG, mode, &found_other_class,
 				    false);
 		  if (__glibc_likely (fd != -1))
-		    {
-		      realname = __strdup (cached);
-		      if (realname == NULL)
-			{
-			  __close (fd);
-			  fd = -1;
-			}
-		    }
+		    realname = cached;
+		  else
+		    free (cached);
 		}
 	    }
 	}
diff --git a/elf/dl-open.c b/elf/dl-open.c
index dec3d32..ae699a9 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -217,7 +217,9 @@  dl_open_worker (void *a)
 	args->nsid = call_map->l_ns;
     }
 
-  assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
+  /* One might be tempted to assert that we are RT_CONSISTENT at this point, but that
+     may not be true if this is a recursive call to dlopen.  */
+  _dl_debug_initialize (0, args->nsid);
 
   /* Load the named object.  */
   struct link_map *new;
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index d07eaac..77f26d4 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -905,8 +905,8 @@  extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
      internal_function;
 
 /* Look up NAME in ld.so.cache and return the file name stored there,
-   or null if none is found.  */
-extern const char *_dl_load_cache_lookup (const char *name)
+   or null if none is found.  Caller must free returned string.  */
+extern char *_dl_load_cache_lookup (const char *name)
      internal_function;
 
 /* If the system does not support MAP_COPY we cannot leave the file open