elf: Signal RT_CONSISTENT after relocation processing in dlopen (bug 31986)

Previously, a la_activity audit event was generated before
relocation processing completed.  This does did not match what
happened during initial startup in elf/rtld.c (towards the end
of dl_main).  It also caused various problems if an auditor
tried to open the same shared object again using dlmopen:
If it was the directly loaded object, it had a search scope
associated with it, so the early exit in dl_open_worker_begin
was taken even though the object was unrelocated.  This caused
the r_state == RT_CONSISTENT assert to fail.  Avoidance of the
assert also depends on reversing the order of r_state update
and auditor event (already implemented in a previous commit).

At the later point, args->map can be NULL due to failure,
so use the assigned namespace ID instead if that is available.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

elf/Makefile

@@ -414,6 +414,7 @@ tests += \
   tst-dlmopen1 \
   tst-dlmopen3 \
   tst-dlmopen4 \
+  tst-dlopen-auditdup \
   tst-dlopen-recurse \
   tst-dlopen-self \
   tst-dlopen-tlsmodid \
@@ -866,6 +867,8 @@ modules-names += \
   tst-dlmopen-twice-mod1 \
   tst-dlmopen-twice-mod2 \
   tst-dlmopen1mod \
+  tst-dlopen-auditdup-auditmod \
+  tst-dlopen-auditdupmod \
   tst-dlopen-recursemod1 \
   tst-dlopen-recursemod2 \
   tst-dlopen-tlsreinitmod1 \
@@ -3159,3 +3162,6 @@ tst-dlopen-tlsreinit4-ENV = LD_AUDIT=$(objpfx)tst-auditmod1.so
 
 $(objpfx)tst-dlopen-recurse.out: $(objpfx)tst-dlopen-recursemod1.so
 $(objpfx)tst-dlopen-recursemod1.so: $(objpfx)tst-dlopen-recursemod2.so
+tst-dlopen-auditdup-ENV = LD_AUDIT=$(objpfx)tst-dlopen-auditdup-auditmod.so
+$(objpfx)tst-dlopen-auditdup.out: \
+  $(objpfx)tst-dlopen-auditdupmod.so $(objpfx)tst-dlopen-auditdup-auditmod.so

elf/dl-open.c

@@ -565,6 +565,14 @@ dl_open_worker_begin (void *a)
 	_dl_debug_printf ("opening file=%s [%lu]; direct_opencount=%u\n\n",
 			  new->l_name, new->l_ns, new->l_direct_opencount);
 
+#ifdef SHARED
+      /* No relocation processing on this execution path.  But
+	 relocation has not been performed for static
+	 position-dependent executables, so disable the assert for
+	 static linking.  */
+      assert (new->l_relocated);
+#endif
+
       /* 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.  */
@@ -586,10 +594,6 @@ dl_open_worker_begin (void *a)
       if ((mode & RTLD_GLOBAL) && new->l_global == 0)
 	add_to_global_update (new);
 
-      const int r_state __attribute__ ((unused))
-        = _dl_debug_update (args->nsid)->r_state;
-      assert (r_state == RT_CONSISTENT);
-
       /* Do not return without calling the (supposedly new) map's
 	 constructor.  This case occurs if a dependency of a directly
 	 opened map has a constructor that calls dlopen again on the
@@ -628,17 +632,6 @@ dl_open_worker_begin (void *a)
 #endif
       }
 
-  /* Notify the debugger all new objects are now ready to go.  */
-  struct r_debug *r = _dl_debug_update (args->nsid);
-  r->r_state = RT_CONSISTENT;
-  _dl_debug_state ();
-  LIBC_PROBE (map_complete, 3, args->nsid, r, new);
-
-#ifdef SHARED
-  /* Auditing checkpoint: we have added all objects.  */
-  _dl_audit_activity_nsid (new->l_ns, LA_ACT_CONSISTENT);
-#endif
-
   _dl_open_check (new);
 
   /* Print scope information.  */
@@ -685,6 +678,7 @@ dl_open_worker_begin (void *a)
      created dlmopen namespaces.  Do not do this for static dlopen
      because libc has relocations against ld.so, which may not have
      been relocated at this point.  */
+  struct r_debug *r = _dl_debug_update (args->nsid);
 #ifdef SHARED
   if (GL(dl_ns)[args->nsid].libc_map != NULL)
     _dl_open_relocate_one_object (args, r, GL(dl_ns)[args->nsid].libc_map,
@@ -776,6 +770,26 @@ dl_open_worker (void *a)
 
     __rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
 
+    /* Auditing checkpoint and debugger signalling.  Do this even on
+       error, so that dlopen exists with consistent state.  */
+    if (args->nsid >= 0 || args->map != NULL)
+      {
+	Lmid_t nsid = args->map != NULL ? args->map->l_ns : args->nsid;
+	struct r_debug *r = _dl_debug_update (nsid);
+#ifdef SHARED
+	bool was_not_consistent  = r->r_state != RT_CONSISTENT;
+#endif
+	r->r_state = RT_CONSISTENT;
+	_dl_debug_state ();
+	LIBC_PROBE (map_complete, 3, nsid, r, new);
+
+#ifdef SHARED
+	if (was_not_consistent)
+	  /* Avoid redudant/recursive signalling.  */
+	  _dl_audit_activity_nsid (nsid, LA_ACT_CONSISTENT);
+#endif
+      }
+
     if (__glibc_unlikely (ex.errstring != NULL))
       /* Reraise the error.  */
       _dl_signal_exception (err, &ex, NULL);

elf/tst-dlopen-auditdup-auditmod.c

@@ -0,0 +1,100 @@
+/* Auditor that opens again an object that just has been opened.
+   Copyright (C) 2024 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 <link.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+unsigned int
+la_version (unsigned int v)
+{
+  return LAV_CURRENT;
+}
+
+static bool trigger_on_la_activity;
+
+unsigned int
+la_objopen (struct link_map *map, Lmid_t lmid, uintptr_t *cookie)
+{
+  printf ("info: la_objopen: \"%s\"\n", map->l_name);
+  if (strstr (map->l_name, "/tst-dlopen-auditdupmod.so") != NULL)
+    trigger_on_la_activity = true;
+  return 0;
+}
+
+void
+la_activity (uintptr_t *cookie, unsigned int flag)
+{
+  static unsigned int calls;
+  ++calls;
+  printf ("info: la_activity: call %u (flag %u)\n", calls, flag);
+  fflush (stdout);
+  if (trigger_on_la_activity)
+    {
+      /* Avoid triggering on the dlmopen call below.  */
+      static bool recursion;
+      if (recursion)
+        return;
+      recursion = true;
+
+      puts ("info: about to dlmopen tst-dlopen-auditdupmod.so");
+      fflush (stdout);
+      void *handle = dlmopen (LM_ID_BASE, "tst-dlopen-auditdupmod.so",
+                              RTLD_NOW);
+      if (handle == NULL)
+        {
+          printf ("error: dlmopen: %s\n", dlerror ());
+          fflush (stdout);
+          _exit (1);
+        }
+
+      /* Check that the constructor has run.  */
+      int *status = dlsym (handle, "auditdupmod_status");
+      if (status == NULL)
+        {
+          printf ("error: dlsym: %s\n", dlerror ());
+          fflush (stdout);
+          _exit (1);
+        }
+      printf ("info: auditdupmod_status == %d\n", *status);
+      if (*status != 1)
+        {
+          puts ("error: auditdupmod_status == 1 expected");
+          fflush (stdout);
+          _exit (1);
+        }
+      /* Checked in the destructor and the main program.  */
+      ++*status;
+      printf ("info: auditdupmod_status == %d\n", *status);
+
+      /* Check that the module has been relocated.  */
+      int **status_address = dlsym (handle, "auditdupmod_status_address");
+      if (status_address == NULL || *status_address != status)
+        {
+          puts ("error: invalid auditdupmod_status address in"
+                " tst-dlopen-auditdupmod.so");
+          fflush (stdout);
+          _exit (1);
+        }
+
+      fflush (stdout);
+    }
+}

elf/tst-dlopen-auditdup.c

@@ -0,0 +1,36 @@
+/* Test that recursive dlopen from auditor works (bug 31986).
+   Copyright (C) 2024 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 <stdio.h>
+#include <support/check.h>
+#include <support/xdlfcn.h>
+
+static int
+do_test (void)
+{
+  puts ("info: about to dlopen tst-dlopen-auditdupmod.so");
+  fflush (stdout);
+  void *handle = xdlopen ("tst-dlopen-auditdupmod.so", RTLD_NOW);
+  int *status = xdlsym (handle, "auditdupmod_status");
+  printf ("info: auditdupmod_status == %d (from main)\n", *status);
+  TEST_COMPARE (*status, 2);
+  xdlclose (handle);
+  return 0;
+}
+
+#include <support/test-driver.c>

elf/tst-dlopen-auditdupmod.c

@@ -0,0 +1,48 @@
+/* Directly opened test module that gets reopened from the auditor.
+   Copyright (C) 2024 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 <stdio.h>
+#include <stdlib.h>
+#include <support/xdlfcn.h>
+
+int auditdupmod_status;
+
+/* Used to check for successful relocation processing.  */
+int *auditdupmod_status_address = &auditdupmod_status;
+
+static void __attribute__ ((constructor))
+init (void)
+{
+  ++auditdupmod_status;
+  printf ("info: tst-dlopen-auditdupmod.so constructor called (status %d)\n",
+          auditdupmod_status);
+}
+
+static void __attribute__ ((destructor))
+fini (void)
+{
+  /* The tst-dlopen-auditdup-auditmod.so auditor incremented
+     auditdupmod_status.  */
+  printf ("info: tst-dlopen-auditdupmod.so destructor called (status %d)\n",
+          auditdupmod_status);
+  if (auditdupmod_status != 2)
+    {
+      puts ("error: auditdupmod_status == 2 expected");
+      exit (1);
+    }
+}