[review,v3] Remove all loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]
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Message ID 20191115160205.9EEC928171@gnutoolchain-gerrit.osci.io
State New
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  • [review,v3] Remove all loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]
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Commit Message

Adhemerval Zanella (Code Review) Nov. 15, 2019, 4:02 p.m. UTC
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471
......................................................................

Remove all loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]

This introduces a “pending NODELETE” state in the link map, which is
flipped to the persistent NODELETE state late in dlopen, via
activate_nodelete.    During initial relocation, symbol binding
records pending NODELETE state only.  dlclose ignores pending NODELETE
state.  Taken together, this results that a partially completed dlopen
is rolled back completely because new NODELETE mappings are unloaded.

Tested on x86_64-linux-gnu and i386-linux-gnu.

Change-Id: Ib2a3d86af6f92d75baca65431d74783ee0dbc292
---
M elf/Makefile
M elf/dl-close.c
M elf/dl-lookup.c
M elf/dl-open.c
M elf/get-dynamic-info.h
A elf/tst-dlopenfail.c
A elf/tst-dlopenfaillinkmod.c
A elf/tst-dlopenfailmod1.c
A elf/tst-dlopenfailmod2.c
M include/link.h
10 files changed, 328 insertions(+), 38 deletions(-)

Comments

Florian Weimer Dec. 2, 2019, 4:07 p.m. UTC | #1
* Florian Weimer:

> +/* Mark the objects as NODELETE if required.  This is delayed until
> +   after dlopen failure is not possible, so that _dl_close can clean
> +   up objects if necessary.  */
> +static void
> +activate_nodelete (struct link_map *new, int mode)
> +{
> +  if (mode & RTLD_NODELETE || new->l_nodelete == link_map_nodelete_pending)
> +    {
> +      if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
> +	_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
> +			  new->l_name, new->l_ns);
> +      new->l_nodelete = link_map_nodelete_active;
> +    }
> +
> +  for (unsigned int i = 0; i < new->l_searchlist.r_nlist; ++i)
> +    {
> +      struct link_map *imap = new->l_searchlist.r_list[i];
> +      if (imap->l_nodelete == link_map_nodelete_pending)
> +	{
> +	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
> +	    _dl_debug_printf ("activating NODELETE for %s [%lu]\n",
> +			      imap->l_name, imap->l_ns);
> +
> +	  /* Only new objects should have set
> +	     link_map_nodelete_pending.  Existing objects should not
> +	     have gained any new dependencies and therefore cannot
> +	     reach NODELETE status.  */
> +	  assert (!imap->l_init_called || imap->l_type != lt_loaded);

This assert is incorrect because the NODELETE markers actually go in the
other direction (from new loaded libraries to their dependencies).

I still need to write tests for this.  But I can submit a patch for the
removal of the assert immediately, if so desired.

Thanks,
Florian
Carlos O'Donell Dec. 2, 2019, 4:53 p.m. UTC | #2
On 12/2/19 11:07 AM, Florian Weimer wrote:
> * Florian Weimer:
> 
>> +/* Mark the objects as NODELETE if required.  This is delayed until
>> +   after dlopen failure is not possible, so that _dl_close can clean
>> +   up objects if necessary.  */
>> +static void
>> +activate_nodelete (struct link_map *new, int mode)
>> +{
>> +  if (mode & RTLD_NODELETE || new->l_nodelete == link_map_nodelete_pending)
>> +    {
>> +      if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
>> +	_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
>> +			  new->l_name, new->l_ns);
>> +      new->l_nodelete = link_map_nodelete_active;
>> +    }
>> +
>> +  for (unsigned int i = 0; i < new->l_searchlist.r_nlist; ++i)
>> +    {
>> +      struct link_map *imap = new->l_searchlist.r_list[i];
>> +      if (imap->l_nodelete == link_map_nodelete_pending)
>> +	{
>> +	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
>> +	    _dl_debug_printf ("activating NODELETE for %s [%lu]\n",
>> +			      imap->l_name, imap->l_ns);
>> +
>> +	  /* Only new objects should have set
>> +	     link_map_nodelete_pending.  Existing objects should not
>> +	     have gained any new dependencies and therefore cannot
>> +	     reach NODELETE status.  */
>> +	  assert (!imap->l_init_called || imap->l_type != lt_loaded);
> 
> This assert is incorrect because the NODELETE markers actually go in the
> other direction (from new loaded libraries to their dependencies).
> 
> I still need to write tests for this.  But I can submit a patch for the
> removal of the assert immediately, if so desired.

I'm happy with seeing two patches, one which fixes the regression for
Fedora Rawhide and OpenSUSE Tumbleweed, and another which expands the
testsuite coverage.

If I understood correctly it's because:

- A dlopen of libstdc++ ...
- Can be used by something else dlopen'd later with a STB_GNU_UNIQUE symbol...
- Causing libstdc++ to be marked NODLETE.

So libstdc++ is l_type == lt_loaded, and l_init_called == 1, which means bot
sides of the || are false.

Patch
diff mbox series

diff --git a/elf/Makefile b/elf/Makefile
index 571f12f..9296162 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -193,7 +193,7 @@ 
 	 tst-debug1 tst-main1 tst-absolute-sym tst-absolute-zero tst-big-note \
 	 tst-unwind-ctor tst-unwind-main tst-audit13 \
 	 tst-sonamemove-link tst-sonamemove-dlopen tst-dlopen-tlsmodid \
-	 tst-dlopen-self tst-auditmany tst-initfinilazyfail
+	 tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
@@ -285,7 +285,8 @@ 
 		tst-auditmanymod1 tst-auditmanymod2 tst-auditmanymod3 \
 		tst-auditmanymod4 tst-auditmanymod5 tst-auditmanymod6 \
 		tst-auditmanymod7 tst-auditmanymod8 tst-auditmanymod9 \
-		tst-initlazyfailmod tst-finilazyfailmod
+		tst-initlazyfailmod tst-finilazyfailmod \
+		tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2
 # Most modules build with _ISOMAC defined, but those filtered out
 # depend on internal headers.
 modules-names-tests = $(filter-out ifuncmod% tst-libc_dlvsym-dso tst-tlsmod%,\
@@ -1591,3 +1592,13 @@ 
   -Wl,-z,lazy -Wl,--unresolved-symbols=ignore-all
 LDFLAGS-tst-finilazyfailmod.so = \
   -Wl,-z,lazy -Wl,--unresolved-symbols=ignore-all
+
+$(objpfx)tst-dlopenfail: $(libdl)
+$(objpfx)tst-dlopenfail.out: \
+  $(objpfx)tst-dlopenfailmod1.so $(objpfx)tst-dlopenfailmod2.so
+# Order matters here.  tst-dlopenfaillinkmod.so's soname ensures
+# a run-time loader failure.
+$(objpfx)tst-dlopenfailmod1.so: \
+  $(shared-thread-library) $(objpfx)tst-dlopenfaillinkmod.so
+LDFLAGS-tst-dlopenfaillinkmod.so = -Wl,-soname,tst-dlopenfail-missingmod.so
+$(objpfx)tst-dlopenfailmod2.so: $(shared-thread-library)
diff --git a/elf/dl-close.c b/elf/dl-close.c
index 33486b9..e35a62d 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -168,14 +168,6 @@ 
   char done[nloaded];
   struct link_map *maps[nloaded];
 
-  /* Clear DF_1_NODELETE to force object deletion.  We don't need to touch
-     l_tls_dtor_count because forced object deletion only happens when an
-     error occurs during object load.  Destructor registration for TLS
-     non-POD objects should not have happened till then for this
-     object.  */
-  if (force)
-    map->l_flags_1 &= ~DF_1_NODELETE;
-
   /* Run over the list and assign indexes to the link maps and enter
      them into the MAPS array.  */
   int idx = 0;
@@ -205,7 +197,7 @@ 
       /* Check whether this object is still used.  */
       if (l->l_type == lt_loaded
 	  && l->l_direct_opencount == 0
-	  && (l->l_flags_1 & DF_1_NODELETE) == 0
+	  && l->l_nodelete != link_map_nodelete_active
 	  /* See CONCURRENCY NOTES in cxa_thread_atexit_impl.c to know why
 	     acquire is sufficient and correct.  */
 	  && atomic_load_acquire (&l->l_tls_dtor_count) == 0
@@ -288,7 +280,7 @@ 
       if (!used[i])
 	{
 	  assert (imap->l_type == lt_loaded
-		  && (imap->l_flags_1 & DF_1_NODELETE) == 0);
+		  && imap->l_nodelete != link_map_nodelete_active);
 
 	  /* Call its termination function.  Do not do it for
 	     half-cooked objects.  Temporarily disable exception
@@ -838,7 +830,7 @@ 
      before we took the lock. There is no way to detect this (see below)
      so we proceed assuming this isn't the case.  First see whether we
      can remove the object at all.  */
-  if (__glibc_unlikely (map->l_flags_1 & DF_1_NODELETE))
+  if (__glibc_unlikely (map->l_nodelete == link_map_nodelete_active))
     {
       /* Nope.  Do nothing.  */
       __rtld_lock_unlock_recursive (GL(dl_load_lock));
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index aaaf437..a2e85a5 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -192,9 +192,10 @@ 
    Return the matching symbol in RESULT.  */
 static void
 do_lookup_unique (const char *undef_name, uint_fast32_t new_hash,
-		  const struct link_map *map, struct sym_val *result,
+		  struct link_map *map, struct sym_val *result,
 		  int type_class, const ElfW(Sym) *sym, const char *strtab,
-		  const ElfW(Sym) *ref, const struct link_map *undef_map)
+		  const ElfW(Sym) *ref, const struct link_map *undef_map,
+		  int flags)
 {
   /* We have to determine whether we already found a symbol with this
      name before.  If not then we have to add it to the search table.
@@ -222,7 +223,7 @@ 
 		     copy from the copy addressed through the
 		     relocation.  */
 		  result->s = sym;
-		  result->m = (struct link_map *) map;
+		  result->m = map;
 		}
 	      else
 		{
@@ -311,9 +312,19 @@ 
                         new_hash, strtab + sym->st_name, sym, map);
 
       if (map->l_type == lt_loaded)
-	/* Make sure we don't unload this object by
-	   setting the appropriate flag.  */
-	((struct link_map *) map)->l_flags_1 |= DF_1_NODELETE;
+	{
+	  /* Make sure we don't unload this object by
+	     setting the appropriate flag.  */
+	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
+	      && map->l_nodelete == link_map_nodelete_inactive)
+	    _dl_debug_printf ("\
+marking %s [%lu] as NODELETE due to unique symbol\n",
+			      map->l_name, map->l_ns);
+	  if (flags & DL_LOOKUP_FOR_RELOCATE)
+	    map->l_nodelete = link_map_nodelete_pending;
+	  else
+	    map->l_nodelete = link_map_nodelete_active;
+	}
     }
   ++tab->n_elements;
 
@@ -525,8 +536,9 @@ 
 	      return 1;
 
 	    case STB_GNU_UNIQUE:;
-	      do_lookup_unique (undef_name, new_hash, map, result, type_class,
-				sym, strtab, ref, undef_map);
+	      do_lookup_unique (undef_name, new_hash, (struct link_map *) map,
+				result, type_class, sym, strtab, ref,
+				undef_map, flags);
 	      return 1;
 
 	    default:
@@ -568,9 +580,13 @@ 
   if (undef_map == map)
     return 0;
 
-  /* Avoid references to objects which cannot be unloaded anyway.  */
+  /* Avoid references to objects which cannot be unloaded anyway.  We
+     do not need to record dependencies if this object goes away
+     during dlopen failure, either.  IFUNC resolvers with relocation
+     dependencies may pick an dependency which can be dlclose'd, but
+     such IFUNC resolvers are undefined anyway.  */
   assert (map->l_type == lt_loaded);
-  if ((map->l_flags_1 & DF_1_NODELETE) != 0)
+  if (map->l_nodelete != link_map_nodelete_inactive)
     return 0;
 
   struct link_map_reldeps *l_reldeps
@@ -678,16 +694,33 @@ 
 
       /* Redo the NODELETE check, as when dl_load_lock wasn't held
 	 yet this could have changed.  */
-      if ((map->l_flags_1 & DF_1_NODELETE) != 0)
+      if (map->l_nodelete != link_map_nodelete_inactive)
 	goto out;
 
       /* If the object with the undefined reference cannot be removed ever
 	 just make sure the same is true for the object which contains the
 	 definition.  */
       if (undef_map->l_type != lt_loaded
-	  || (undef_map->l_flags_1 & DF_1_NODELETE) != 0)
+	  || (undef_map->l_nodelete != link_map_nodelete_inactive))
 	{
-	  map->l_flags_1 |= DF_1_NODELETE;
+	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
+	      && map->l_nodelete == link_map_nodelete_inactive)
+	    {
+	      if (undef_map->l_name[0] == '\0')
+		_dl_debug_printf ("\
+marking %s [%lu] as NODELETE due to reference to main program\n",
+				  map->l_name, map->l_ns);
+	      else
+		_dl_debug_printf ("\
+marking %s [%lu] as NODELETE due to reference to %s [%lu]\n",
+				  map->l_name, map->l_ns,
+				  undef_map->l_name, undef_map->l_ns);
+	    }
+
+	  if (flags & DL_LOOKUP_FOR_RELOCATE)
+	    map->l_nodelete = link_map_nodelete_pending;
+	  else
+	    map->l_nodelete = link_map_nodelete_active;
 	  goto out;
 	}
 
@@ -712,7 +745,18 @@ 
 		 no fatal problem.  We simply make sure the referenced object
 		 cannot be unloaded.  This is semantically the correct
 		 behavior.  */
-	      map->l_flags_1 |= DF_1_NODELETE;
+	      if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
+		  && map->l_nodelete == link_map_nodelete_inactive)
+		_dl_debug_printf ("\
+marking %s [%lu] as NODELETE due to memory allocation failure\n",
+				  map->l_name, map->l_ns);
+	      if (flags & DL_LOOKUP_FOR_RELOCATE)
+		/* In case of non-lazy binding, we could actually
+		   report the memory allocation error, but for now, we
+		   use the conservative approximation as well. */
+		map->l_nodelete = link_map_nodelete_pending;
+	      else
+		map->l_nodelete = link_map_nodelete_active;
 	      goto out;
 	    }
 	  else
diff --git a/elf/dl-open.c b/elf/dl-open.c
index 89954bd..db870ed 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -410,6 +410,40 @@ 
     }
 }
 
+/* Mark the objects as NODELETE if required.  This is delayed until
+   after dlopen failure is not possible, so that _dl_close can clean
+   up objects if necessary.  */
+static void
+activate_nodelete (struct link_map *new, int mode)
+{
+  if (mode & RTLD_NODELETE || new->l_nodelete == link_map_nodelete_pending)
+    {
+      if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
+	_dl_debug_printf ("activating NODELETE for %s [%lu]\n",
+			  new->l_name, new->l_ns);
+      new->l_nodelete = link_map_nodelete_active;
+    }
+
+  for (unsigned int i = 0; i < new->l_searchlist.r_nlist; ++i)
+    {
+      struct link_map *imap = new->l_searchlist.r_list[i];
+      if (imap->l_nodelete == link_map_nodelete_pending)
+	{
+	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES))
+	    _dl_debug_printf ("activating NODELETE for %s [%lu]\n",
+			      imap->l_name, imap->l_ns);
+
+	  /* Only new objects should have set
+	     link_map_nodelete_pending.  Existing objects should not
+	     have gained any new dependencies and therefore cannot
+	     reach NODELETE status.  */
+	  assert (!imap->l_init_called || imap->l_type != lt_loaded);
+
+	  imap->l_nodelete = link_map_nodelete_active;
+	}
+     }
+}
+
 /* struct dl_init_args and call_dl_init are used to call _dl_init with
    exception handling disabled.  */
 struct dl_init_args
@@ -479,12 +513,6 @@ 
       return;
     }
 
-  /* Mark the object as not deletable if the RTLD_NODELETE flags was passed.
-     Do this early so that we don't skip marking the object if it was
-     already loaded.  */
-  if (__glibc_unlikely (mode & RTLD_NODELETE))
-    new->l_flags_1 |= DF_1_NODELETE;
-
   if (__glibc_unlikely (mode & __RTLD_SPROF))
     /* This happens only if we load a DSO for 'sprof'.  */
     return;
@@ -500,19 +528,37 @@ 
 	_dl_debug_printf ("opening file=%s [%lu]; direct_opencount=%u\n\n",
 			  new->l_name, new->l_ns, new->l_direct_opencount);
 
-      /* If the user requested the object to be in the global namespace
-	 but it is not so far, add it now.  */
+      /* If the user requested the object to be in the global
+	 namespace but it is not so far, prepare to add it now.  This
+	 can raise an exception to do a malloc failure.  */
       if ((mode & RTLD_GLOBAL) && new->l_global == 0)
+	add_to_global_resize (new);
+
+      /* Mark the object as not deletable if the RTLD_NODELETE flags
+	 was passed.  */
+      if (__glibc_unlikely (mode & RTLD_NODELETE))
 	{
-	  add_to_global_resize (new);
-	  add_to_global_update (new);
+	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_FILES)
+	      && new->l_nodelete == link_map_nodelete_inactive)
+	    _dl_debug_printf ("marking %s [%lu] as NODELETE\n",
+			      new->l_name, new->l_ns);
+	  new->l_nodelete = link_map_nodelete_active;
 	}
 
+      /* Finalize the addition to the global scope.  */
+      if ((mode & RTLD_GLOBAL) && new->l_global == 0)
+	add_to_global_update (new);
+
       assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
 
       return;
     }
 
+  /* Schedule NODELETE marking for the directly loaded object if
+     requested.  */
+  if (__glibc_unlikely (mode & RTLD_NODELETE))
+    new->l_nodelete = link_map_nodelete_pending;
+
   /* Load that object's dependencies.  */
   _dl_map_object_deps (new, NULL, 0, 0,
 		       mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT));
@@ -587,6 +633,14 @@ 
 
   int relocation_in_progress = 0;
 
+  /* Perform relocation.  This can trigger lazy binding in IFUNC
+     resolvers.  For NODELETE mappings, these dependencies are not
+     recorded because the flag has not been applied to the newly
+     loaded objects.  This means that upon dlopen failure, these
+     NODELETE objects can be unloaded despite existing references to
+     them.  However, such relocation dependencies in IFUNC resolvers
+     are undefined anyway, so this is not a problem.  */
+
   for (unsigned int i = nmaps; i-- > 0; )
     {
       l = maps[i];
@@ -616,7 +670,7 @@ 
 	      _dl_start_profile ();
 
 	      /* Prevent unloading the object.  */
-	      GL(dl_profile_map)->l_flags_1 |= DF_1_NODELETE;
+	      GL(dl_profile_map)->l_nodelete = link_map_nodelete_active;
 	    }
 	}
       else
@@ -647,6 +701,8 @@ 
      All memory allocations for new objects must have happened
      before.  */
 
+  activate_nodelete (new, mode);
+
   /* Second stage after resize_scopes: Actually perform the scope
      update.  After this, dlsym and lazy binding can bind to new
      objects.  */
@@ -805,6 +861,10 @@ 
 	    GL(dl_tls_dtv_gaps) = true;
 
 	  _dl_close_worker (args.map, true);
+
+	  /* All link_map_nodelete_pending objects should have been
+	     deleted at this point, which is why it is not necessary
+	     to reset the flag here.  */
 	}
 
       assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index af9dd57..075683d 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -163,6 +163,8 @@ 
   if (info[VERSYMIDX (DT_FLAGS_1)] != NULL)
     {
       l->l_flags_1 = info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val;
+      if (l->l_flags_1 & DF_1_NODELETE)
+	l->l_nodelete = link_map_nodelete_pending;
 
       /* Only DT_1_SUPPORTED_MASK bits are supported, and we would like
 	 to assert this, but we can't. Users have been setting
diff --git a/elf/tst-dlopenfail.c b/elf/tst-dlopenfail.c
new file mode 100644
index 0000000..ce3140c
--- /dev/null
+++ b/elf/tst-dlopenfail.c
@@ -0,0 +1,79 @@ 
+/* Test dlopen rollback after failures involving NODELETE objects (bug 20839).
+   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; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <errno.h>
+#include <gnu/lib-names.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/xdlfcn.h>
+
+static int
+do_test (void)
+{
+  /* This test uses libpthread as the canonical NODELETE module.  If
+     libpthread is no longer NODELETE because it has been merged into
+     libc, the test needs to be updated.  */
+  TEST_VERIFY (dlsym (NULL, "pthread_create") == NULL);
+
+  /* This is expected to fail because of the missing dependency.  */
+  puts ("info: attempting to load tst-dlopenfailmod1.so");
+  TEST_VERIFY (dlopen ("tst-dlopenfailmod1.so", RTLD_LAZY) == NULL);
+  const char *message = dlerror ();
+  TEST_COMPARE_STRING (message,
+                       "tst-dlopenfail-missingmod.so:"
+                       " cannot open shared object file:"
+                       " No such file or directory");
+
+  /* Do not probe for the presence of libpthread at this point because
+     that might trigger relocation if bug 20839 is present, obscuring
+     a subsequent crash.  */
+
+  /* This is expected to succeed.  */
+  puts ("info: loading tst-dlopenfailmod2.so");
+  void *handle = xdlopen ("tst-dlopenfailmod2.so", RTLD_NOW);
+  xdlclose (handle);
+
+  /* libpthread should remain loaded.  */
+  TEST_VERIFY (dlopen (LIBPTHREAD_SO, RTLD_LAZY | RTLD_NOLOAD) != NULL);
+  TEST_VERIFY (dlsym (NULL, "pthread_create") == NULL);
+
+  /* We can make libpthread global, and then the symbol should become
+     available.  */
+  TEST_VERIFY (dlopen (LIBPTHREAD_SO, RTLD_LAZY | RTLD_GLOBAL) != NULL);
+  TEST_VERIFY (dlsym (NULL, "pthread_create") != NULL);
+
+  /* sem_open is sufficiently complex to depend on relocations.  */
+  void *(*sem_open_ptr) (const char *, int flag, ...)
+    = dlsym (NULL, "sem_open");
+  if (sem_open_ptr == NULL)
+    /* Hurd does not implement sem_open.  */
+    puts ("warning: sem_open not found, further testing not possible");
+  else
+    {
+      errno = 0;
+      TEST_VERIFY (sem_open_ptr ("/", 0) == NULL);
+      TEST_COMPARE (errno, EINVAL);
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-dlopenfaillinkmod.c b/elf/tst-dlopenfaillinkmod.c
new file mode 100644
index 0000000..3b14b02
--- /dev/null
+++ b/elf/tst-dlopenfaillinkmod.c
@@ -0,0 +1,17 @@ 
+/* Empty module with a soname which is not available at run time.
+   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; if not, see
+   <https://www.gnu.org/licenses/>.  */
diff --git a/elf/tst-dlopenfailmod1.c b/elf/tst-dlopenfailmod1.c
new file mode 100644
index 0000000..6ef4882
--- /dev/null
+++ b/elf/tst-dlopenfailmod1.c
@@ -0,0 +1,36 @@ 
+/* Module which depends on two modules: one NODELETE, one missing.
+   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; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Note: Due to the missing second module, this object cannot be
+   loaded at run time.  */
+
+#include <pthread.h>
+#include <stdio.h>
+#include <unistd.h>
+
+/* Force linking against libpthread.  */
+void *pthread_create_reference = pthread_create;
+
+/* The constructor will never be executed because the module cannot be
+   loaded.  */
+static void __attribute__ ((constructor))
+init (void)
+{
+  puts ("tst-dlopenfailmod1 constructor executed");
+  _exit (1);
+}
diff --git a/elf/tst-dlopenfailmod2.c b/elf/tst-dlopenfailmod2.c
new file mode 100644
index 0000000..7d60038
--- /dev/null
+++ b/elf/tst-dlopenfailmod2.c
@@ -0,0 +1,29 @@ 
+/* Module which depends on on a NODELETE module, and can be loaded.
+   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; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <pthread.h>
+#include <stdio.h>
+
+/* Force linking against libpthread.  */
+void *pthread_create_reference = pthread_create;
+
+static void __attribute__ ((constructor))
+init (void)
+{
+  puts ("info: tst-dlopenfailmod2.so constructor invoked");
+}
diff --git a/include/link.h b/include/link.h
index be52b97..2e771e4 100644
--- a/include/link.h
+++ b/include/link.h
@@ -79,6 +79,21 @@ 
     int malloced;
   };
 
+/* Type used by the l_nodelete member.  */
+enum link_map_nodelete
+{
+ /* This link map can be deallocated.  */
+ link_map_nodelete_inactive = 0, /* Zero-initialized in _dl_new_object.  */
+
+ /* This link map cannot be deallocated.  */
+ link_map_nodelete_active,
+
+ /* This link map cannot be deallocated after dlopen has succeded.
+    dlopen turns this into link_map_nodelete_active.  dlclose treats
+    this intermediate state as link_map_nodelete_active.  */
+ link_map_nodelete_pending,
+};
+
 
 /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
    members form a chain of all the shared objects loaded at startup.
@@ -203,6 +218,11 @@ 
 				       freed, ie. not allocated with
 				       the dummy malloc in ld.so.  */
 
+    /* Actually of type enum link_map_nodelete.  Separate byte due to
+       a read in add_dependency in elf/dl-lookup.c outside the loader
+       lock.  Only valid for l_type == lt_loaded.  */
+    unsigned char l_nodelete;
+
 #include <link_map.h>
 
     /* Collected information about own RPATH directories.  */