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nptl: pthread_kill, pthread_cancel should not fail after exit (bug 19193)

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This closes one remaining race condition related to bug 12889: if
the thread already exited on the kernel side, returning ESRCH
is not correct because that error is reserved for the thread IDs
(pthread_t values) whose lifetime has ended.  In case of a
kernel-side exit and a valid thread ID, no signal needs to be sent
and cancellation does not have an effect, so just return 0.

sysdeps/pthread/tst-kill4.c triggers undefined behavior and is
removed with this commit.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
(cherry picked from commit 8af8456004)
This commit is contained in:
Florian Weimer 2021-09-13 11:06:08 +02:00
parent addc9d62d6
commit 3abf3bd4ed
7 changed files with 107 additions and 96 deletions
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1
NEWS
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@ -9,6 +9,7 @@ Version 2.34.1
The following bugs are resolved with this release:
[19193] nptl: pthread_kill, pthread_cancel should not fail after exit
[28182] _TIME_BITS=64 in C++ has issues with fcntl, ioctl, prctl

9
nptl/pthread_cancel.c
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@ -62,10 +62,11 @@ __pthread_cancel (pthread_t th)
{
volatile struct pthread *pd = (volatile struct pthread *) th;
/* Make sure the descriptor is valid. */
if (INVALID_TD_P (pd))
/* Not a valid thread handle. */
return ESRCH;
if (pd->tid == 0)
/* The thread has already exited on the kernel side. Its outcome
(regular exit, other cancelation) has already been
determined. */
return 0;
static int init_sigcancel = 0;
if (atomic_load_relaxed (&init_sigcancel) == 0)

7
nptl/pthread_kill.c
View File

@ -46,7 +46,12 @@ __pthread_kill_internal (pthread_t threadid, int signo)
? INTERNAL_SYSCALL_ERRNO (val) : 0);
}
else
val = ESRCH;
/* The kernel reports that the thread has exited. POSIX specifies
the ESRCH error only for the case when the lifetime of a thread
ID has ended, but calling pthread_kill on such a thread ID is
undefined in glibc. Therefore, do not treat kernel thread exit
as an error. */
val = 0;
return val;
}

5
sysdeps/pthread/Makefile
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@ -89,7 +89,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
tst-join8 tst-join9 tst-join10 tst-join11 tst-join12 tst-join13 \
tst-join14 tst-join15 \
tst-key1 tst-key2 tst-key3 tst-key4 \
tst-kill1 tst-kill2 tst-kill3 tst-kill4 tst-kill5 tst-kill6 \
tst-kill1 tst-kill2 tst-kill3 tst-kill5 tst-kill6 \
tst-locale1 tst-locale2 \
tst-memstream \
tst-mutex-errorcheck tst-mutex1 tst-mutex2 tst-mutex3 tst-mutex4 \
@ -118,6 +118,9 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
tst-unload \
tst-unwind-thread \
tst-pt-vfork1 tst-pt-vfork2 tst-vfork1x tst-vfork2x \
tst-pthread_cancel-exited \
tst-pthread_kill-exited \
# tests
tests-time64 := \
tst-abstime-time64 \

90
sysdeps/pthread/tst-kill4.c
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@ -1,90 +0,0 @@
/* Copyright (C) 2003-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
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 <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
static void *
tf (void *a)
{
return NULL;
}
int
do_test (void)
{
pthread_attr_t at;
if (pthread_attr_init (&at) != 0)
{
puts ("attr_create failed");
exit (1);
}
/* Limit thread stack size, because if it is too large, pthread_join
will free it immediately rather than put it into stack cache. */
if (pthread_attr_setstacksize (&at, 2 * 1024 * 1024) != 0)
{
puts ("setstacksize failed");
exit (1);
}
pthread_t th;
if (pthread_create (&th, &at, tf, NULL) != 0)
{
puts ("create failed");
exit (1);
}
pthread_attr_destroy (&at);
if (pthread_join (th, NULL) != 0)
{
puts ("join failed");
exit (1);
}
/* The following only works because we assume here something about
the implementation. Namely, that the memory allocated for the
thread descriptor is not going away, that the TID field is
cleared and therefore the signal is sent to process 0, and that
we can savely assume there is no other process with this ID at
that time. */
int e = pthread_kill (th, 0);
if (e == 0)
{
puts ("pthread_kill succeeded");
exit (1);
}
if (e != ESRCH)
{
puts ("pthread_kill didn't return ESRCH");
exit (1);
}
return 0;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"

45
sysdeps/pthread/tst-pthread_cancel-exited.c Normal file
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@ -0,0 +1,45 @@
/* Test that pthread_kill succeeds for an exited thread.
Copyright (C) 2021 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/>. */
/* This test verifies that pthread_kill returns 0 (and not ESRCH) for
a thread that has exited on the kernel side. */
#include <stddef.h>
#include <support/support.h>
#include <support/xthread.h>
static void *
noop_thread (void *closure)
{
return NULL;
}
static int
do_test (void)
{
pthread_t thr = xpthread_create (NULL, noop_thread, NULL);
support_wait_for_thread_exit ();
xpthread_cancel (thr);
xpthread_join (thr);
return 0;
}
#include <support/test-driver.c>

46
sysdeps/pthread/tst-pthread_kill-exited.c Normal file
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@ -0,0 +1,46 @@
/* Test that pthread_kill succeeds for an exited thread.
Copyright (C) 2021 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/>. */
/* This test verifies that pthread_kill returns 0 (and not ESRCH) for
a thread that has exited on the kernel side. */
#include <signal.h>
#include <stddef.h>
#include <support/support.h>
#include <support/xthread.h>
static void *
noop_thread (void *closure)
{
return NULL;
}
static int
do_test (void)
{
pthread_t thr = xpthread_create (NULL, noop_thread, NULL);
support_wait_for_thread_exit ();
xpthread_kill (thr, SIGUSR1);
xpthread_join (thr);
return 0;
}
#include <support/test-driver.c>