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eae81d7057
The choice between the kill vs tgkill system calls is not just about
the TID reuse race, but also about whether the signal is sent to the
whole process (and any thread in it) or to a specific thread.
This was caught by the openposix test suite:
LTP: openposix test suite - FAIL: SIGUSR1 is member of new thread pendingset.
<https://gitlab.com/cki-project/kernel-tests/-/issues/764>
Fixes commit 526c3cf11e ("nptl: Fix race
between pthread_kill and thread exit (bug 12889)").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
113 lines
4.1 KiB
C
113 lines
4.1 KiB
C
/* Send a signal to a specific pthread. Stub version.
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Copyright (C) 2014-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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<https://www.gnu.org/licenses/>. */
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#include <libc-lock.h>
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#include <unistd.h>
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#include <pthreadP.h>
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#include <shlib-compat.h>
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/* Sends SIGNO to THREADID. If the thread is about to exit or has
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already exited on the kernel side, return NO_TID. Otherwise return
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0 or an error code. */
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static int
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__pthread_kill_implementation (pthread_t threadid, int signo, int no_tid)
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{
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struct pthread *pd = (struct pthread *) threadid;
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if (pd == THREAD_SELF)
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{
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/* Use the actual TID from the kernel, so that it refers to the
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current thread even if called after vfork. There is no
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signal blocking in this case, so that the signal is delivered
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immediately, before __pthread_kill_internal returns: a signal
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sent to the thread itself needs to be delivered
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synchronously. (It is unclear if Linux guarantees the
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delivery of all pending signals after unblocking in the code
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below. POSIX only guarantees delivery of a single signal,
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which may not be the right one.) */
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pid_t tid = INTERNAL_SYSCALL_CALL (gettid);
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int ret = INTERNAL_SYSCALL_CALL (tgkill, __getpid (), tid, signo);
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return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
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}
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/* Block all signals, as required by pd->exit_lock. */
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sigset_t old_mask;
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__libc_signal_block_all (&old_mask);
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__libc_lock_lock (pd->exit_lock);
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int ret;
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if (pd->exiting)
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/* The thread is about to exit (or has exited). Sending the
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signal is either not observable (the target thread has already
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blocked signals at this point), or it will fail, or it might be
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delivered to a new, unrelated thread that has reused the TID.
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So do not actually send the signal. */
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ret = no_tid;
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else
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{
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ret = INTERNAL_SYSCALL_CALL (tgkill, __getpid (), pd->tid, signo);
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ret = INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
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}
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__libc_lock_unlock (pd->exit_lock);
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__libc_signal_restore_set (&old_mask);
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return ret;
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}
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int
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__pthread_kill_internal (pthread_t threadid, int signo)
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{
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/* Do not report an error in the no-tid case because the threadid
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argument is still valid (the thread ID lifetime has not ended),
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and ESRCH (for example) would be misleading. */
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return __pthread_kill_implementation (threadid, signo, 0);
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}
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int
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__pthread_kill (pthread_t threadid, int signo)
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{
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/* Disallow sending the signal we use for cancellation, timers,
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for the setxid implementation. */
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if (__is_internal_signal (signo))
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return EINVAL;
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return __pthread_kill_internal (threadid, signo);
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}
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/* Some architectures (for instance arm) might pull raise through libgcc, so
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avoid the symbol version if it ends up being used on ld.so. */
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#if !IS_IN(rtld)
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libc_hidden_def (__pthread_kill)
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versioned_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_34);
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# if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
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/* Variant which returns ESRCH in the no-TID case, for backwards
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compatibility. */
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int
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attribute_compat_text_section
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__pthread_kill_esrch (pthread_t threadid, int signo)
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{
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if (__is_internal_signal (signo))
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return EINVAL;
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return __pthread_kill_implementation (threadid, signo, ESRCH);
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}
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compat_symbol (libc, __pthread_kill_esrch, pthread_kill, GLIBC_2_0);
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# endif
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#endif
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