This is the mail archive of the libc-alpha@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[PATCH v3 1/3] elf: Allow dlopen of filter object to work [BZ #16272]


There are two fixes that are needed to be able to dlopen filter
objects. First _dl_map_object_deps cannot assume that map will be at
the beginning of l_searchlist.r_list[], as filtees are inserted before
map. Secondly dl_open_worker needs to ensure that filtees get
relocated.

In _dl_map_object_deps:

* avoiding removing relocatiion dependencies of map by setting
  l_reserved to 0 and otherwise processing the rest of the search
  list.

* ensure that map remains at the beginning of l_initfini - the list
  of things that need initialisation (and destruction). Do this by
  splitting the copy up. This may not be required, but matches the
  initialization order without dlopen.

Modify dl_open_worker to relocate the objects in new->l_inifini.
new->l_initfini is constructed in _dl_map_object_deps, and lists the
objects that need initialization and destruction. Originally the list
of objects in new->l_next are relocated. All of these objects should
also be included in new->l_initfini (both lists are populated with
dependencies in _dl_map_object_deps). We can't use new->l_prev to pick
up filtees, as during a recursive dlopen from an interposed malloc
call, l->prev can contain objects that are not ready for relocation.

Add tests to verify that symbols resolve to the filtee implementation
when filter objects are used, both as a normal link and when dlopen'd.

Tested by running the testsuite on x86_64.
---
 elf/Makefile               | 12 ++++++++++--
 elf/dl-deps.c              | 35 ++++++++++++++++++++++++++---------
 elf/dl-open.c              | 11 +++++++----
 elf/tst-filterobj-dlopen.c | 39 +++++++++++++++++++++++++++++++++++++++
 elf/tst-filterobj-flt.c    | 24 ++++++++++++++++++++++++
 elf/tst-filterobj-lib.c    | 24 ++++++++++++++++++++++++
 elf/tst-filterobj-lib.h    | 18 ++++++++++++++++++
 elf/tst-filterobj.c        | 36 ++++++++++++++++++++++++++++++++++++
 8 files changed, 184 insertions(+), 15 deletions(-)
 create mode 100644 elf/tst-filterobj-dlopen.c
 create mode 100644 elf/tst-filterobj-flt.c
 create mode 100644 elf/tst-filterobj-lib.c
 create mode 100644 elf/tst-filterobj-lib.h
 create mode 100644 elf/tst-filterobj.c

diff --git a/elf/Makefile b/elf/Makefile
index 0debea7..69f11c7 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -199,7 +199,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 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-dlopenfail
+	 tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail \
+	 tst-filterobj tst-filterobj-dlopen
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
@@ -292,7 +293,8 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-auditmanymod4 tst-auditmanymod5 tst-auditmanymod6 \
 		tst-auditmanymod7 tst-auditmanymod8 tst-auditmanymod9 \
 		tst-initlazyfailmod tst-finilazyfailmod \
-		tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2
+		tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2 \
+		tst-filterobj-flt tst-filterobj-lib
 # 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%,\
@@ -1627,3 +1629,9 @@ $(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: $(shared-thread-library)
+
+LDFLAGS-tst-filterobj-flt.so = -Wl,--filter=$(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj: $(objpfx)tst-filterobj-flt.so | $(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj-dlopen: $(libdl) | $(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj.out: $(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj-dlopen.out: $(objpfx)tst-filterobj-lib.so
diff --git a/elf/dl-deps.c b/elf/dl-deps.c
index c29b988..bb85c83 100644
--- a/elf/dl-deps.c
+++ b/elf/dl-deps.c
@@ -550,13 +550,14 @@ Filters not supported with LD_TRACE_PRELINKING"));
     }
 
   /* Maybe we can remove some relocation dependencies now.  */
-  assert (map->l_searchlist.r_list[0] == map);
   struct link_map_reldeps *l_reldeps = NULL;
   if (map->l_reldeps != NULL)
     {
-      for (i = 1; i < nlist; ++i)
+      for (i = 0; i < nlist; ++i)
 	map->l_searchlist.r_list[i]->l_reserved = 1;
 
+      /* Avoid removing relocation dependencies of the main binary.  */
+      map->l_reserved = 0;
       struct link_map **list = &map->l_reldeps->list[0];
       for (i = 0; i < map->l_reldeps->act; ++i)
 	if (list[i]->l_reserved)
@@ -581,16 +582,32 @@ Filters not supported with LD_TRACE_PRELINKING"));
 	      }
 	  }
 
-      for (i = 1; i < nlist; ++i)
+      for (i = 0; i < nlist; ++i)
 	map->l_searchlist.r_list[i]->l_reserved = 0;
     }
 
-  /* Sort the initializer list to take dependencies into account.  The binary
-     itself will always be initialize last.  */
-  memcpy (l_initfini, map->l_searchlist.r_list,
-	  nlist * sizeof (struct link_map *));
-  /* We can skip looking for the binary itself which is at the front of
-     the search list.  */
+  /* Sort the initializer list to take dependencies into account.  Always
+     initialize the binary itself last.  First, find it in the search list.  */
+  for (i = 0; i < nlist; ++i)
+    if (map->l_searchlist.r_list[i] == map)
+      break;
+  assert (i < nlist);
+  if (i > 0)
+    {
+      /* Copy the binary into position 0.  */
+      memcpy (l_initfini, &map->l_searchlist.r_list[i],
+	      sizeof (struct link_map *));
+      /* Copy the filtees.  */
+      memcpy (&l_initfini[1], map->l_searchlist.r_list,
+	      i * sizeof (struct link_map *));
+      /* Copy the remainder.  */
+      memcpy (&l_initfini[i + 1], &map->l_searchlist.r_list[i + 1],
+	      (nlist - i - 1) * sizeof (struct link_map *));
+    }
+  else
+    memcpy (l_initfini, map->l_searchlist.r_list,
+	    nlist * sizeof (struct link_map *));
+
   _dl_sort_maps (&l_initfini[1], nlist - 1, NULL, false);
 
   /* Terminate the list of dependencies.  */
diff --git a/elf/dl-open.c b/elf/dl-open.c
index df9f29a..9996fe9 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -637,22 +637,25 @@ dl_open_worker (void *a)
      allows IFUNC relocations to work and it also means copy
      relocation of dependencies are if necessary overwritten.  */
   unsigned int nmaps = 0;
-  struct link_map *l = new;
+  unsigned int j = 0;
+  struct link_map *l = new->l_initfini[0];
   do
     {
       if (! l->l_real->l_relocated)
 	++nmaps;
-      l = l->l_next;
+      l = new->l_initfini[++j];
     }
   while (l != NULL);
+  /* Stack allocation is limited by the number of loaded objects.  */
   struct link_map *maps[nmaps];
   nmaps = 0;
-  l = new;
+  j = 0;
+  l = new->l_initfini[0];
   do
     {
       if (! l->l_real->l_relocated)
 	maps[nmaps++] = l;
-      l = l->l_next;
+      l = new->l_initfini[++j];
     }
   while (l != NULL);
   _dl_sort_maps (maps, nmaps, NULL, false);
diff --git a/elf/tst-filterobj-dlopen.c b/elf/tst-filterobj-dlopen.c
new file mode 100644
index 0000000..81eed0f
--- /dev/null
+++ b/elf/tst-filterobj-dlopen.c
@@ -0,0 +1,39 @@
+/* Test for BZ16272, dlopen'ing a filter object.
+   Ensure that symbols from the filter object resolve to the filtee.
+
+   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 <stdio.h>
+#include "support/check.h"
+#include "support/xdlfcn.h"
+
+static int do_test (void)
+{
+  void *lib = xdlopen ("tst-filterobj-flt.so", RTLD_LAZY);
+  char *(*fn)(void) = xdlsym (lib, "get_text");
+  const char* text = fn ();
+
+  printf ("%s\n", text);
+
+  /* Verify the text matches what we expect from the filtee */
+  TEST_COMPARE_STRING (text, "Hello from filtee (PASS)");
+
+  return 0;
+}
+
+#include "support/test-driver.c"
diff --git a/elf/tst-filterobj-flt.c b/elf/tst-filterobj-flt.c
new file mode 100644
index 0000000..b4e10b2
--- /dev/null
+++ b/elf/tst-filterobj-flt.c
@@ -0,0 +1,24 @@
+/* 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 "tst-filterobj-lib.h"
+
+/* We never want to see the output of the filter object */
+const char *get_text (void)
+{
+  return "Hello from filter object (FAIL)";
+}
diff --git a/elf/tst-filterobj-lib.c b/elf/tst-filterobj-lib.c
new file mode 100644
index 0000000..07e2348
--- /dev/null
+++ b/elf/tst-filterobj-lib.c
@@ -0,0 +1,24 @@
+/* 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 "tst-filterobj-lib.h"
+
+/* This is the real implementation that wants to be called */
+const char *get_text (void)
+{
+  return "Hello from filtee (PASS)";
+}
diff --git a/elf/tst-filterobj-lib.h b/elf/tst-filterobj-lib.h
new file mode 100644
index 0000000..bed9bf8
--- /dev/null
+++ b/elf/tst-filterobj-lib.h
@@ -0,0 +1,18 @@
+/* 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/>.  */
+
+const char *get_text (void);
diff --git a/elf/tst-filterobj.c b/elf/tst-filterobj.c
new file mode 100644
index 0000000..d38eb9b
--- /dev/null
+++ b/elf/tst-filterobj.c
@@ -0,0 +1,36 @@
+/* Test that symbols from filter objects are resolved to the filtee.
+
+   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 <stdio.h>
+#include "support/check.h"
+#include "tst-filterobj-lib.h"
+
+static int do_test (void)
+{
+  const char* text = get_text ();
+
+  printf ("%s\n", text);
+
+  /* Verify the text matches what we expect from the filtee */
+  TEST_COMPARE_STRING (text, "Hello from filtee (PASS)");
+
+  return 0;
+}
+
+#include "support/test-driver.c"
-- 
2.7.4


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]