Re: [PATCH] Report dlsym, dlvsym lookup errors using dlerror [BZ #19509]

[Florian Weimer <fweimer at redhat dot com>]

On 03/31/2016 01:50 AM, Carlos O'Donell wrote:
> On 03/30/2016 07:53 AM, Florian Weimer wrote:
>> On 02/09/2016 03:31 PM, Florian Weimer wrote:
>>> 2016-02-09  Florian Weimer  <fweimer@redhat.com>
>>>
>>> 	[BZ #19509]
>>> 	* elf/dl-lookup.c (_dl_lookup_symbol_x): Report error even if
>>> 	skip_map != NULL.
>>> 	* elf/bug19509.c: New file.
>>> 	* elf/Makefile (tests): Add bug19509.
>>> 	(bug19509): Link against libdl.
>>
>> Ping?
>>
>>   https://sourceware.org/ml/libc-alpha/2016-02/msg00172.html
> 
> I agree. The only caller with non-NULL skip_map is:
> 
> 146   else if (handle == RTLD_NEXT)
> 147     {
> 148       if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded))
> 149         {
> 150           if (match == NULL
> 151               || caller < match->l_map_start
> 152               || caller >= match->l_map_end)
> 153             GLRO(dl_signal_error) (0, NULL, NULL, N_("\
> 154 RTLD_NEXT used in code not dynamically loaded"));
> 155         }
> 156 
> 157       struct link_map *l = match;
> 158       while (l->l_loader != NULL)
> 159         l = l->l_loader;
> 160 
> 161       result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope,
> 162                                          vers, 0, 0, match);
> 163     }
> 
> Whose purpose it is to skip the current map for lookup.
> 
> Your patch and testcase look good to me.

Thanks, here is what I committed.  I renamed the test case based on
previous comments on other threads.

Thanks,
Florian

2016-03-31  Florian Weimer  <fweimer@redhat.com>

	[BZ #19509]
	* elf/dl-lookup.c (_dl_lookup_symbol_x): Report error even if
	skip_map != NULL.
	* elf/tst-dlsym-error.c: New file.
	* elf/Makefile (tests): Add tst-dlsym-error.
	(tst-dlsym-error): Link against libdl.

diff --git a/elf/Makefile b/elf/Makefile
index 7b6d6d7..bb23d93 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -149,7 +149,7 @@ tests += loadtest restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-nodelete) \
 	 tst-initorder tst-initorder2 tst-relsort1 tst-null-argv \
 	 tst-ptrguard1 tst-tlsalign tst-tlsalign-extern tst-nodelete-opened \
-	 tst-nodelete2 tst-audit11 tst-audit12
+	 tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error
 #	 reldep9
 ifeq ($(build-hardcoded-path-in-tests),yes)
 tests += tst-dlopen-aout
@@ -1257,3 +1257,5 @@ $(objpfx)tst-prelink-cmp.out: tst-prelink.exp \
 $(objpfx)tst-ldconfig-X.out : tst-ldconfig-X.sh $(objpfx)ldconfig
 	$(SHELL) $< '$(common-objpfx)' '$(test-wrapper)' '$(test-wrapper-env)' > $@; \
 	$(evaluate-test)
+
+$(objpfx)tst-dlsym-error: $(libdl)
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index f577759..6d299c1 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -858,7 +858,6 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
   if (__glibc_unlikely (current_value.s == NULL))
     {
       if ((*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
-	  && skip_map == NULL
 	  && !(GLRO(dl_debug_mask) & DL_DEBUG_UNUSED))
 	{
 	  /* We could find no value for a strong reference.  */
diff --git a/elf/tst-dlsym-error.c b/elf/tst-dlsym-error.c
new file mode 100644
index 0000000..11b0358
--- /dev/null
+++ b/elf/tst-dlsym-error.c
@@ -0,0 +1,113 @@
+/* Test error reporting for dlsym, dlvsym failures.
+   Copyright (C) 2016 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <gnu/lib-names.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/* Used to disambiguate symbol names.  */
+static int counter;
+
+static void
+test_one (void *handle, const char *name, void *(func) (void *, const char *),
+          const char *suffix)
+{
+  ++counter;
+  char symbol[32];
+  snprintf (symbol, sizeof (symbol), "no_such_symbol_%d", counter);
+  char *expected_message;
+  if (asprintf (&expected_message, ": undefined symbol: %s%s",
+                symbol, suffix) < 0)
+    {
+      printf ("error: asprintf: %m\n");
+      abort ();
+    }
+
+  void *addr = func (handle, symbol);
+  if (addr != NULL)
+    {
+      printf ("error: %s: found symbol \"no_such_symbol\"\n", name);
+      abort ();
+    }
+  const char *message = dlerror ();
+  if (message == NULL)
+    {
+      printf ("error: %s: missing error message\n", name);
+      abort ();
+    }
+  const char *message_without_path = strchrnul (message, ':');
+  if (strcmp (message_without_path, expected_message) != 0)
+    {
+      printf ("error: %s: unexpected error message: %s\n", name, message);
+      abort ();
+    }
+  free (expected_message);
+
+  message = dlerror ();
+  if (message != NULL)
+    {
+      printf ("error: %s: unexpected error message: %s\n", name, message);
+      abort ();
+    }
+}
+
+static void
+test_handles (const char *name, void *(func) (void *, const char *),
+              const char *suffix)
+{
+  test_one (RTLD_DEFAULT, name, func, suffix);
+  test_one (RTLD_NEXT, name, func, suffix);
+
+  void *handle = dlopen (LIBC_SO, RTLD_LAZY);
+  if (handle == NULL)
+    {
+      printf ("error: cannot dlopen %s: %s\n", LIBC_SO, dlerror ());
+      abort ();
+    }
+  test_one (handle, name, func, suffix);
+  dlclose (handle);
+}
+
+static void *
+dlvsym_no_such_version (void *handle, const char *name)
+{
+  return dlvsym (handle, name, "NO_SUCH_VERSION");
+}
+
+static void *
+dlvsym_glibc_private (void *handle, const char *name)
+{
+  return dlvsym (handle, name, "GLIBC_PRIVATE");
+}
+
+static int
+do_test (void)
+{
+  test_handles ("dlsym", dlsym, "");
+  test_handles ("dlvsym", dlvsym_no_such_version,
+                ", version NO_SUCH_VERSION");
+  test_handles ("dlvsym", dlvsym_glibc_private,
+                ", version GLIBC_PRIVATE");
+
+  return 0;
+}
+
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"