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Fix recursive dlopen.
The ability to recursively call dlopen is useful for malloc implementations that wish to load other dynamic modules that implement reentrant/AS-safe functions to use in their own implementation. Given that a user malloc implementation may be called by an ongoing dlopen to allocate memory the user malloc implementation interrupts dlopen and if it calls dlopen again that's a reentrant call. This patch fixes the issues with the ld.so.cache mapping and the _r_debug assertion which prevent this from working as expected. See: https://sourceware.org/ml/libc-alpha/2014-12/msg00446.html
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19
ChangeLog
19
ChangeLog
@ -1,3 +1,22 @@
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2015-01-21 Carlos O'Donell <carlos@redhat.com>
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[BZ #17702]
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* dlfcn/Makefile (tests): Add tst-rec-dlopen.
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(modules-names): Add moddummy1 and moddummy2.
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($(objpfx)tst-rec-dlopen): Define.
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* dlfcn/moddummy1.c: New file.
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* dlfcn/moddummy2.c: New file.
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* dlfcn/tst-rec-dlopen.c: New file.
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* elf/dl-cache.c (_dl_load_cache_lookup):
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Return char*. Copy result with alloca/strcpy/strdup.
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* elf/dl-load.c (_dl_map_object): _dl_load_cached_lookup
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returns char*. Free cached. If not saving realname
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free cached.
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* elf/dl-open.c (dl_open_worker): Do not assert that
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_r_debug->r_state is RT_CONSISTENT.
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* sysdeps/generic/ldsodefs.h: _dl_load_cache_lookup
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returns char*.
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2015-01-21 Torvald Riegel <triegel@redhat.com>
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Carlos O'Donell <carlos@redhat.com>
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7
NEWS
7
NEWS
@ -15,9 +15,10 @@ Version 2.21
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17485, 17501, 17506, 17508, 17522, 17555, 17570, 17571, 17572, 17573,
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17574, 17582, 17583, 17584, 17585, 17589, 17594, 17601, 17608, 17616,
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17625, 17630, 17633, 17634, 17635, 17647, 17653, 17657, 17658, 17664,
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17665, 17668, 17682, 17717, 17719, 17722, 17723, 17724, 17725, 17732,
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17733, 17744, 17745, 17746, 17747, 17748, 17775, 17777, 17780, 17781,
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17782, 17791, 17793, 17796, 17797, 17803, 17806, 17834, 17844, 17848
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17665, 17668, 17682, 17702, 17717, 17719, 17722, 17723, 17724, 17725,
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17732, 17733, 17744, 17745, 17746, 17747, 17748, 17775, 17777, 17780,
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17781, 17782, 17791, 17793, 17796, 17797, 17803, 17806, 17834, 17844,
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17848
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* A new semaphore algorithm has been implemented in generic C code for all
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machines. Previous custom assembly implementations of semaphore were
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@ -36,13 +36,13 @@ endif
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ifeq (yes,$(build-shared))
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tests = glrefmain failtest tst-dladdr default errmsg1 tstcxaatexit \
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bug-dlopen1 bug-dlsym1 tst-dlinfo bug-atexit1 bug-atexit2 \
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bug-atexit3 tstatexit bug-dl-leaf
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bug-atexit3 tstatexit bug-dl-leaf tst-rec-dlopen
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endif
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modules-names = glreflib1 glreflib2 glreflib3 failtestmod defaultmod1 \
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defaultmod2 errmsg1mod modatexit modcxaatexit \
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bug-dlsym1-lib1 bug-dlsym1-lib2 bug-atexit1-lib \
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bug-atexit2-lib bug-atexit3-lib bug-dl-leaf-lib \
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bug-dl-leaf-lib-cb
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bug-dl-leaf-lib-cb moddummy1 moddummy2
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failtestmod.so-no-z-defs = yes
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glreflib2.so-no-z-defs = yes
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@ -139,3 +139,6 @@ $(objpfx)bug-dl-leaf: $(objpfx)bug-dl-leaf-lib.so
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$(objpfx)bug-dl-leaf.out: $(objpfx)bug-dl-leaf-lib-cb.so
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$(objpfx)bug-dl-leaf-lib.so: $(libdl)
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$(objpfx)bug-dl-leaf-lib-cb.so: $(objpfx)bug-dl-leaf-lib.so
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$(objpfx)tst-rec-dlopen: $(libdl)
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$(objpfx)tst-rec-dlopen.out: $(objpfx)moddummy1.so $(objpfx)moddummy2.so
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10
dlfcn/moddummy1.c
Normal file
10
dlfcn/moddummy1.c
Normal file
@ -0,0 +1,10 @@
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/* Provide a dummy DSO for tst-rec-dlopen to use. */
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#include <stdio.h>
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#include <stdlib.h>
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int
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dummy1 (void)
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{
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printf ("Called dummy1()\n");
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return 1;
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}
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13
dlfcn/moddummy2.c
Normal file
13
dlfcn/moddummy2.c
Normal file
@ -0,0 +1,13 @@
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/* Provide a dummy DSO for tst-rec-dlopen to use. */
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#include <stdio.h>
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#include <stdlib.h>
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int
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dummy2 (void)
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{
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printf ("Called dummy2()\n");
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/* If the outer dlopen is not dummy1 (becuase of some error)
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then tst-rec-dlopen will see a value of -1 as the returned
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result and fail. */
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return -1;
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}
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144
dlfcn/tst-rec-dlopen.c
Normal file
144
dlfcn/tst-rec-dlopen.c
Normal file
@ -0,0 +1,144 @@
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/* Test recursive dlopen using malloc hooks.
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Copyright (C) 1998-2014 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <stdio.h>
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#include <stdlib.h>
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#include <malloc.h>
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#include <dlfcn.h>
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#define DSO "moddummy1.so"
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#define FUNC "dummy1"
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#define DSO1 "moddummy2.so"
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#define FUNC1 "dummy2"
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/* Result of the called function. */
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int func_result;
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/* Prototype for my hook. */
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void *custom_malloc_hook (size_t, const void *);
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/* Pointer to old malloc hooks. */
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void *(*old_malloc_hook) (size_t, const void *);
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/* Call function func_name in DSO dso_name via dlopen. */
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void
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call_func (const char *dso_name, const char *func_name)
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{
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int ret;
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void *dso;
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int (*func) (void);
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char *err;
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/* Open the DSO. */
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dso = dlopen (dso_name, RTLD_NOW|RTLD_GLOBAL);
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if (dso == NULL)
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{
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err = dlerror ();
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fprintf (stderr, "%s\n", err);
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exit (1);
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}
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/* Clear any errors. */
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dlerror ();
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/* Lookup func. */
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*(void **) (&func) = dlsym (dso, func_name);
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if (func == NULL)
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{
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err = dlerror ();
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if (err != NULL)
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{
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fprintf (stderr, "%s\n", err);
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exit (1);
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}
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}
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/* Call func. */
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func_result = (*func) ();
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/* Close the library and look for errors too. */
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ret = dlclose (dso);
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if (ret != 0)
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{
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err = dlerror ();
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fprintf (stderr, "%s\n", err);
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exit (1);
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}
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}
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/* Empty hook that does nothing. */
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void *
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custom_malloc_hook (size_t size, const void *caller)
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{
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void *result;
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/* Restore old hooks. */
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__malloc_hook = old_malloc_hook;
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/* First call a function in another library via dlopen. */
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call_func (DSO1, FUNC1);
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/* Called recursively. */
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result = malloc (size);
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/* Restore new hooks. */
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__malloc_hook = custom_malloc_hook;
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return result;
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}
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static int
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do_test (void)
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{
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/* Save old hook. */
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old_malloc_hook = __malloc_hook;
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/* Install new hook. */
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__malloc_hook = custom_malloc_hook;
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/* Bug 17702 fixes two things:
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* A recursive dlopen unmapping the ld.so.cache.
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* An assertion that _r_debug is RT_CONSISTENT at entry to dlopen.
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We can only test the latter. Testing the former requires modifying
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ld.so.conf to cache the dummy libraries, then running ldconfig,
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then run the test. If you do all of that (and glibc's test
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infrastructure doesn't support that yet) then the test will
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SEGFAULT without the fix. If you don't do that, then the test
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will abort because of the assert described in detail below. */
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call_func (DSO, FUNC);
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/* Restore old hook. */
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__malloc_hook = old_malloc_hook;
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/* The function dummy2() is called by the malloc hook. Check to
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see that it was called. This ensures the second recursive
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dlopen happened and we called the function in that library.
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Before the fix you either get a SIGSEGV when accessing mmap'd
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ld.so.cache data or an assertion failure about _r_debug not
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beint RT_CONSISTENT. We don't test for the SIGSEGV since it
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would require finding moddummy1 or moddummy2 in the cache and
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we don't have any infrastructure to test that, but the _r_debug
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assertion triggers. */
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printf ("Returned result is %d\n", func_result);
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if (func_result <= 0)
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{
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printf ("FAIL: Function call_func() not called.\n");
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exit (1);
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}
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printf ("PASS: Function call_func() called more than once.\n");
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return 0;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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/* Look up NAME in ld.so.cache and return the file name stored there, or null
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if none is found. The cache is loaded if it was not already. If loading
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the cache previously failed there will be no more attempts to load it. */
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const char *
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the cache previously failed there will be no more attempts to load it.
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The caller is responsible for freeing the returned string. The ld.so.cache
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may be unmapped at any time by a completing recursive dlopen and
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this function must take care that it does not return references to
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any data in the mapping. */
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char *
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internal_function
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_dl_load_cache_lookup (const char *name)
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{
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@ -289,7 +292,17 @@ _dl_load_cache_lookup (const char *name)
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&& best != NULL)
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_dl_debug_printf (" trying file=%s\n", best);
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return best;
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if (best == NULL)
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return NULL;
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/* The double copy is *required* since malloc may be interposed
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and call dlopen itself whose completion would unmap the data
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we are accessing. Therefore we must make the copy of the
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mapping data without using malloc. */
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char *temp;
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temp = alloca (strlen (best) + 1);
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strcpy (temp, best);
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return strdup (temp);
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}
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#ifndef MAP_COPY
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{
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/* Check the list of libraries in the file /etc/ld.so.cache,
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for compatibility with Linux's ldconfig program. */
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const char *cached = _dl_load_cache_lookup (name);
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char *cached = _dl_load_cache_lookup (name);
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if (cached != NULL)
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{
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@ -2075,6 +2075,7 @@ _dl_map_object (struct link_map *loader, const char *name,
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if (memcmp (cached, dirp, system_dirs_len[cnt]) == 0)
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{
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/* The prefix matches. Don't use the entry. */
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free (cached);
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cached = NULL;
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break;
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}
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@ -2092,14 +2093,9 @@ _dl_map_object (struct link_map *loader, const char *name,
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LA_SER_CONFIG, mode, &found_other_class,
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false);
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if (__glibc_likely (fd != -1))
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{
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realname = __strdup (cached);
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if (realname == NULL)
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{
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__close (fd);
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fd = -1;
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}
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}
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realname = cached;
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else
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free (cached);
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}
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}
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}
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args->nsid = call_map->l_ns;
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}
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assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
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/* One might be tempted to assert that we are RT_CONSISTENT at this point, but that
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may not be true if this is a recursive call to dlopen. */
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_dl_debug_initialize (0, args->nsid);
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/* Load the named object. */
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struct link_map *new;
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internal_function;
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/* Look up NAME in ld.so.cache and return the file name stored there,
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or null if none is found. */
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extern const char *_dl_load_cache_lookup (const char *name)
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or null if none is found. Caller must free returned string. */
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extern char *_dl_load_cache_lookup (const char *name)
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internal_function;
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/* If the system does not support MAP_COPY we cannot leave the file open
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