diff options
| -rw-r--r-- | include/register-atfork.h | 26 | ||||
| -rw-r--r-- | posix/fork.c | 7 | ||||
| -rw-r--r-- | posix/register-atfork.c | 140 | ||||
| -rw-r--r-- | sysdeps/pthread/Makefile | 38 | ||||
| -rw-r--r-- | sysdeps/pthread/tst-atfork3.c | 118 | ||||
| -rw-r--r-- | sysdeps/pthread/tst-atfork3mod.c | 44 | ||||
| -rw-r--r-- | sysdeps/pthread/tst-atfork4.c | 128 | ||||
| -rw-r--r-- | sysdeps/pthread/tst-atfork4mod.c | 48 |
8 files changed, 499 insertions, 50 deletions
diff --git a/include/register-atfork.h b/include/register-atfork.h index be63113..5ebe5a0 100644 --- a/include/register-atfork.h +++ b/include/register-atfork.h @@ -26,6 +26,7 @@ struct fork_handler void (*parent_handler) (void); void (*child_handler) (void); void *dso_handle; + uint64_t id; }; /* Function to call to unregister fork handlers. */ @@ -39,19 +40,18 @@ enum __run_fork_handler_type atfork_run_parent }; -/* Run the atfork handlers and lock/unlock the internal lock depending - of the WHO argument: - - - atfork_run_prepare: run all the PREPARE_HANDLER in reverse order of - insertion and locks the internal lock. - - atfork_run_child: run all the CHILD_HANDLER and unlocks the internal - lock. - - atfork_run_parent: run all the PARENT_HANDLER and unlocks the internal - lock. - - Perform locking only if DO_LOCKING. */ -extern void __run_fork_handlers (enum __run_fork_handler_type who, - _Bool do_locking) attribute_hidden; +/* Run the atfork prepare handlers in the reverse order of registration and + return the ID of the last registered handler. If DO_LOCKING is true, the + internal lock is held locked upon return. */ +extern uint64_t __run_prefork_handlers (_Bool do_locking) attribute_hidden; + +/* Given a handler type (parent or child), run all the atfork handlers in + the order of registration up to and including the handler with id equal + to LASTRUN. If DO_LOCKING is true, the internal lock is unlocked prior + to return. */ +extern void __run_postfork_handlers (enum __run_fork_handler_type who, + _Bool do_locking, + uint64_t lastrun) attribute_hidden; /* C library side function to register new fork handlers. */ extern int __register_atfork (void (*__prepare) (void), diff --git a/posix/fork.c b/posix/fork.c index 6b50c09..e1be342 100644 --- a/posix/fork.c +++ b/posix/fork.c @@ -46,8 +46,9 @@ __libc_fork (void) best effort to make is async-signal-safe at least for single-thread case. */ bool multiple_threads = __libc_single_threaded == 0; + uint64_t lastrun; - __run_fork_handlers (atfork_run_prepare, multiple_threads); + lastrun = __run_prefork_handlers (multiple_threads); struct nss_database_data nss_database_data; @@ -105,7 +106,7 @@ __libc_fork (void) reclaim_stacks (); /* Run the handlers registered for the child. */ - __run_fork_handlers (atfork_run_child, multiple_threads); + __run_postfork_handlers (atfork_run_child, multiple_threads, lastrun); } else { @@ -123,7 +124,7 @@ __libc_fork (void) } /* Run the handlers registered for the parent. */ - __run_fork_handlers (atfork_run_parent, multiple_threads); + __run_postfork_handlers (atfork_run_parent, multiple_threads, lastrun); if (pid < 0) __set_errno (save_errno); diff --git a/posix/register-atfork.c b/posix/register-atfork.c index 74b1b58..c039fb4 100644 --- a/posix/register-atfork.c +++ b/posix/register-atfork.c @@ -18,6 +18,8 @@ #include <libc-lock.h> #include <stdbool.h> #include <register-atfork.h> +#include <intprops.h> +#include <stdio.h> #define DYNARRAY_ELEMENT struct fork_handler #define DYNARRAY_STRUCT fork_handler_list @@ -26,7 +28,7 @@ #include <malloc/dynarray-skeleton.c> static struct fork_handler_list fork_handlers; -static bool fork_handler_init = false; +static uint64_t fork_handler_counter; static int atfork_lock = LLL_LOCK_INITIALIZER; @@ -36,11 +38,8 @@ __register_atfork (void (*prepare) (void), void (*parent) (void), { lll_lock (atfork_lock, LLL_PRIVATE); - if (!fork_handler_init) - { - fork_handler_list_init (&fork_handlers); - fork_handler_init = true; - } + if (fork_handler_counter == 0) + fork_handler_list_init (&fork_handlers); struct fork_handler *newp = fork_handler_list_emplace (&fork_handlers); if (newp != NULL) @@ -49,6 +48,13 @@ __register_atfork (void (*prepare) (void), void (*parent) (void), newp->parent_handler = parent; newp->child_handler = child; newp->dso_handle = dso_handle; + + /* IDs assigned to handlers start at 1 and increment with handler + registration. Un-registering a handlers discards the corresponding + ID. It is not reused in future registrations. */ + if (INT_ADD_OVERFLOW (fork_handler_counter, 1)) + __libc_fatal ("fork handler counter overflow"); + newp->id = ++fork_handler_counter; } /* Release the lock. */ @@ -103,37 +109,111 @@ __unregister_atfork (void *dso_handle) lll_unlock (atfork_lock, LLL_PRIVATE); } -void -__run_fork_handlers (enum __run_fork_handler_type who, _Bool do_locking) +uint64_t +__run_prefork_handlers (_Bool do_locking) { - struct fork_handler *runp; + uint64_t lastrun; - if (who == atfork_run_prepare) + if (do_locking) + lll_lock (atfork_lock, LLL_PRIVATE); + + /* We run prepare handlers from last to first. After fork, only + handlers up to the last handler found here (pre-fork) will be run. + Handlers registered during __run_prefork_handlers or + __run_postfork_handlers will be positioned after this last handler, and + since their prepare handlers won't be run now, their parent/child + handlers should also be ignored. */ + lastrun = fork_handler_counter; + + size_t sl = fork_handler_list_size (&fork_handlers); + for (size_t i = sl; i > 0;) { - if (do_locking) - lll_lock (atfork_lock, LLL_PRIVATE); - size_t sl = fork_handler_list_size (&fork_handlers); - for (size_t i = sl; i > 0; i--) - { - runp = fork_handler_list_at (&fork_handlers, i - 1); - if (runp->prepare_handler != NULL) - runp->prepare_handler (); - } + struct fork_handler *runp + = fork_handler_list_at (&fork_handlers, i - 1); + + uint64_t id = runp->id; + + if (runp->prepare_handler != NULL) + { + if (do_locking) + lll_unlock (atfork_lock, LLL_PRIVATE); + + runp->prepare_handler (); + + if (do_locking) + lll_lock (atfork_lock, LLL_PRIVATE); + } + + /* We unlocked, ran the handler, and locked again. In the + meanwhile, one or more deregistrations could have occurred leading + to the current (just run) handler being moved up the list or even + removed from the list itself. Since handler IDs are guaranteed to + to be in increasing order, the next handler has to have: */ + + /* A. An earlier position than the current one has. */ + i--; + + /* B. A lower ID than the current one does. The code below skips + any newly added handlers with higher IDs. */ + while (i > 0 + && fork_handler_list_at (&fork_handlers, i - 1)->id >= id) + i--; } - else + + return lastrun; +} + +void +__run_postfork_handlers (enum __run_fork_handler_type who, _Bool do_locking, + uint64_t lastrun) +{ + size_t sl = fork_handler_list_size (&fork_handlers); + for (size_t i = 0; i < sl;) { - size_t sl = fork_handler_list_size (&fork_handlers); - for (size_t i = 0; i < sl; i++) - { - runp = fork_handler_list_at (&fork_handlers, i); - if (who == atfork_run_child && runp->child_handler) - runp->child_handler (); - else if (who == atfork_run_parent && runp->parent_handler) - runp->parent_handler (); - } + struct fork_handler *runp = fork_handler_list_at (&fork_handlers, i); + uint64_t id = runp->id; + + /* prepare handlers were not run for handlers with ID > LASTRUN. + Thus, parent/child handlers will also not be run. */ + if (id > lastrun) + break; + if (do_locking) - lll_unlock (atfork_lock, LLL_PRIVATE); + lll_unlock (atfork_lock, LLL_PRIVATE); + + if (who == atfork_run_child && runp->child_handler) + runp->child_handler (); + else if (who == atfork_run_parent && runp->parent_handler) + runp->parent_handler (); + + if (do_locking) + lll_lock (atfork_lock, LLL_PRIVATE); + + /* We unlocked, ran the handler, and locked again. In the meanwhile, + one or more [de]registrations could have occurred. Due to this, + the list size must be updated. */ + sl = fork_handler_list_size (&fork_handlers); + + /* The just-run handler could also have moved up the list. */ + + if (sl > i && fork_handler_list_at (&fork_handlers, i)->id == id) + /* The position of the recently run handler hasn't changed. The + next handler to be run is an easy increment away. */ + i++; + else + { + /* The next handler to be run is the first handler in the list + to have an ID higher than the current one. */ + for (i = 0; i < sl; i++) + { + if (fork_handler_list_at (&fork_handlers, i)->id > id) + break; + } + } } + + if (do_locking) + lll_unlock (atfork_lock, LLL_PRIVATE); } diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile index e67db42..c725586 100644 --- a/sysdeps/pthread/Makefile +++ b/sysdeps/pthread/Makefile @@ -154,16 +154,36 @@ tests += tst-cancelx2 tst-cancelx3 tst-cancelx6 tst-cancelx8 tst-cancelx9 \ tst-cleanupx0 tst-cleanupx1 tst-cleanupx2 tst-cleanupx3 ifeq ($(build-shared),yes) -tests += tst-atfork2 tst-pt-tls4 tst-_res1 tst-fini1 tst-create1 +tests += \ + tst-atfork2 \ + tst-pt-tls4 \ + tst-_res1 \ + tst-fini1 \ + tst-create1 \ + tst-atfork3 \ + tst-atfork4 \ +# tests + tests-nolibpthread += tst-fini1 endif -modules-names += tst-atfork2mod tst-tls4moda tst-tls4modb \ - tst-_res1mod1 tst-_res1mod2 tst-fini1mod \ - tst-create1mod +modules-names += \ + tst-atfork2mod \ + tst-tls4moda \ + tst-tls4modb \ + tst-_res1mod1 \ + tst-_res1mod2 \ + tst-fini1mod \ + tst-create1mod \ + tst-atfork3mod \ + tst-atfork4mod \ +# module-names + test-modules = $(addprefix $(objpfx),$(addsuffix .so,$(modules-names))) tst-atfork2mod.so-no-z-defs = yes +tst-atfork3mod.so-no-z-defs = yes +tst-atfork4mod.so-no-z-defs = yes tst-create1mod.so-no-z-defs = yes ifeq ($(build-shared),yes) @@ -226,8 +246,18 @@ tst-atfork2-ENV = MALLOC_TRACE=$(objpfx)tst-atfork2.mtrace \ LD_PRELOAD=$(common-objpfx)/malloc/libc_malloc_debug.so $(objpfx)tst-atfork2mod.so: $(shared-thread-library) +$(objpfx)tst-atfork3: $(shared-thread-library) +LDFLAGS-tst-atfork3 = -rdynamic +$(objpfx)tst-atfork3mod.so: $(shared-thread-library) + +$(objpfx)tst-atfork4: $(shared-thread-library) +LDFLAGS-tst-atfork4 = -rdynamic +$(objpfx)tst-atfork4mod.so: $(shared-thread-library) + ifeq ($(build-shared),yes) $(objpfx)tst-atfork2.out: $(objpfx)tst-atfork2mod.so +$(objpfx)tst-atfork3.out: $(objpfx)tst-atfork3mod.so +$(objpfx)tst-atfork4.out: $(objpfx)tst-atfork4mod.so endif ifeq ($(build-shared),yes) diff --git a/sysdeps/pthread/tst-atfork3.c b/sysdeps/pthread/tst-atfork3.c new file mode 100644 index 0000000..bb2250e --- /dev/null +++ b/sysdeps/pthread/tst-atfork3.c @@ -0,0 +1,118 @@ +/* Check if pthread_atfork handler can call dlclose (BZ#24595). + Copyright (C) 2022 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 <stdio.h> +#include <pthread.h> +#include <unistd.h> +#include <stdlib.h> +#include <stdbool.h> + +#include <support/check.h> +#include <support/xthread.h> +#include <support/capture_subprocess.h> +#include <support/xdlfcn.h> + +/* Check if pthread_atfork handlers do not deadlock when calling a function + that might alter the internal fork handle list, such as dlclose. + + The test registers a callback set with pthread_atfork(), dlopen() a shared + library (nptl/tst-atfork3mod.c), calls an exported symbol from the library + (which in turn also registers atfork handlers), and calls fork to trigger + the callbacks. */ + +static void *handler; +static bool run_dlclose_prepare; +static bool run_dlclose_parent; +static bool run_dlclose_child; + +static void +prepare (void) +{ + if (run_dlclose_prepare) + xdlclose (handler); +} + +static void +parent (void) +{ + if (run_dlclose_parent) + xdlclose (handler); +} + +static void +child (void) +{ + if (run_dlclose_child) + xdlclose (handler); +} + +static void +proc_func (void *closure) +{ +} + +static void +do_test_generic (bool dlclose_prepare, bool dlclose_parent, bool dlclose_child) +{ + run_dlclose_prepare = dlclose_prepare; + run_dlclose_parent = dlclose_parent; + run_dlclose_child = dlclose_child; + + handler = xdlopen ("tst-atfork3mod.so", RTLD_NOW); + + int (*atfork3mod_func)(void); + atfork3mod_func = xdlsym (handler, "atfork3mod_func"); + + atfork3mod_func (); + + struct support_capture_subprocess proc + = support_capture_subprocess (proc_func, NULL); + support_capture_subprocess_check (&proc, "tst-atfork3", 0, sc_allow_none); + + handler = atfork3mod_func = NULL; + + support_capture_subprocess_free (&proc); +} + +static void * +thread_func (void *closure) +{ + return NULL; +} + +static int +do_test (void) +{ + { + /* Make the process acts as multithread. */ + pthread_attr_t attr; + xpthread_attr_init (&attr); + xpthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED); + xpthread_create (&attr, thread_func, NULL); + } + + TEST_COMPARE (pthread_atfork (prepare, parent, child), 0); + + do_test_generic (true /* prepare */, false /* parent */, false /* child */); + do_test_generic (false /* prepare */, true /* parent */, false /* child */); + do_test_generic (false /* prepare */, false /* parent */, true /* child */); + + return 0; +} + +#include <support/test-driver.c> diff --git a/sysdeps/pthread/tst-atfork3mod.c b/sysdeps/pthread/tst-atfork3mod.c new file mode 100644 index 0000000..6d0658c --- /dev/null +++ b/sysdeps/pthread/tst-atfork3mod.c @@ -0,0 +1,44 @@ +/* Copyright (C) 2022 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 <unistd.h> +#include <stdlib.h> +#include <pthread.h> + +#include <support/check.h> + +static void +mod_prepare (void) +{ +} + +static void +mod_parent (void) +{ +} + +static void +mod_child (void) +{ +} + +int atfork3mod_func (void) +{ + TEST_COMPARE (pthread_atfork (mod_prepare, mod_parent, mod_child), 0); + + return 0; +} diff --git a/sysdeps/pthread/tst-atfork4.c b/sysdeps/pthread/tst-atfork4.c new file mode 100644 index 0000000..52dc87e --- /dev/null +++ b/sysdeps/pthread/tst-atfork4.c @@ -0,0 +1,128 @@ +/* pthread_atfork supports handlers that call pthread_atfork or dlclose. + Copyright (C) 2022 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 <support/xdlfcn.h> +#include <stdio.h> +#include <support/xthread.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <support/xunistd.h> +#include <support/check.h> +#include <stdlib.h> + +static void * +thread_func (void *x) +{ + return NULL; +} + +static unsigned int second_atfork_handler_runcount = 0; + +static void +second_atfork_handler (void) +{ + second_atfork_handler_runcount++; +} + +static void *h = NULL; + +static unsigned int atfork_handler_runcount = 0; + +static void +prepare (void) +{ + /* These atfork handlers are registered while atfork handlers are being + executed and thus will not be executed during the corresponding + fork. */ + TEST_VERIFY_EXIT (pthread_atfork (second_atfork_handler, + second_atfork_handler, + second_atfork_handler) == 0); + + /* This will de-register the atfork handlers registered by the dlopen'd + library and so they will not be executed. */ + if (h != NULL) + { + xdlclose (h); + h = NULL; + } + + atfork_handler_runcount++; +} + +static void +after (void) +{ + atfork_handler_runcount++; +} + +static int +do_test (void) +{ + /* Make sure __libc_single_threaded is 0. */ + pthread_attr_t attr; + xpthread_attr_init (&attr); + xpthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED); + xpthread_create (&attr, thread_func, NULL); + + void (*reg_atfork_handlers) (void); + + h = xdlopen ("tst-atfork4mod.so", RTLD_LAZY); + + reg_atfork_handlers = xdlsym (h, "reg_atfork_handlers"); + + reg_atfork_handlers (); + + /* We register our atfork handlers *after* loading the module so that our + prepare handler is called first at fork, where we then dlclose the + module before its prepare handler has a chance to be called. */ + TEST_VERIFY_EXIT (pthread_atfork (prepare, after, after) == 0); + + pid_t pid = xfork (); + + /* Both the parent and the child processes should observe this. */ + TEST_VERIFY_EXIT (atfork_handler_runcount == 2); + TEST_VERIFY_EXIT (second_atfork_handler_runcount == 0); + + if (pid > 0) + { + int childstat; + + xwaitpid (-1, &childstat, 0); + TEST_VERIFY_EXIT (WIFEXITED (childstat) + && WEXITSTATUS (childstat) == 0); + + /* This time, the second set of atfork handlers should also be called + since the handlers are already in place before fork is called. */ + + pid = xfork (); + + TEST_VERIFY_EXIT (atfork_handler_runcount == 4); + TEST_VERIFY_EXIT (second_atfork_handler_runcount == 2); + + if (pid > 0) + { + xwaitpid (-1, &childstat, 0); + TEST_VERIFY_EXIT (WIFEXITED (childstat) + && WEXITSTATUS (childstat) == 0); + } + } + + return 0; +} + +#include <support/test-driver.c> diff --git a/sysdeps/pthread/tst-atfork4mod.c b/sysdeps/pthread/tst-atfork4mod.c new file mode 100644 index 0000000..e111efe --- /dev/null +++ b/sysdeps/pthread/tst-atfork4mod.c @@ -0,0 +1,48 @@ +/* pthread_atfork supports handlers that call pthread_atfork or dlclose. + Copyright (C) 2022 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 <stdlib.h> + +/* This dynamically loaded library simply registers its atfork handlers when + asked to. The atfork handlers should never be executed because the + library is unloaded before fork is called by the test program. */ + +static void +prepare (void) +{ + abort (); +} + +static void +parent (void) +{ + abort (); +} + +static void +child (void) +{ + abort (); +} + +void +reg_atfork_handlers (void) +{ + pthread_atfork (prepare, parent, child); +} |