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27d83441a2
The behavior of the signal mask on threads created by timer_create for SIGEV_THREAD timers are implementation-defined and glibc explicit unblocks all signals before calling the user-defined function. This behavior, although not incorrect standard-wise, opens a race if a program using a blocked rt-signal plus sigwaitinfo (and without an installed signal handler for the rt-signal) receives a signal while executing the used-defined function for SIGEV_THREAD. A better alternative discussed in bug report is to rather block all signals (besides the internal ones not available to application usage). This patch fixes this issue by only unblocking SIGSETXID (used on set*uid function) and SIGCANCEL (used for thread cancellation). Checked on x86_64-linux-gnu and i686-linux-gnu.
112 lines
3.2 KiB
C
112 lines
3.2 KiB
C
/* Special use of signals internally. Linux version.
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Copyright (C) 2014-2020 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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#ifndef __INTERNAL_SIGNALS_H
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# define __INTERNAL_SIGNALS_H
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#include <signal.h>
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#include <sigsetops.h>
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#include <stdbool.h>
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#include <limits.h>
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#include <sysdep.h>
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/* The signal used for asynchronous cancelation. */
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#define SIGCANCEL __SIGRTMIN
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/* Signal needed for the kernel-supported POSIX timer implementation.
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We can reuse the cancellation signal since we can distinguish
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cancellation from timer expirations. */
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#define SIGTIMER SIGCANCEL
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/* Signal used to implement the setuid et.al. functions. */
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#define SIGSETXID (__SIGRTMIN + 1)
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/* Return is sig is used internally. */
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static inline bool
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__is_internal_signal (int sig)
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{
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return (sig == SIGCANCEL) || (sig == SIGSETXID);
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}
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/* Remove internal glibc signal from the mask. */
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static inline void
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__clear_internal_signals (sigset_t *set)
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{
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__sigdelset (set, SIGCANCEL);
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__sigdelset (set, SIGSETXID);
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}
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static const sigset_t sigall_set = {
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.__val = {[0 ... _SIGSET_NWORDS-1 ] = -1 }
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};
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static const sigset_t sigtimer_set = {
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.__val = { [0] = __sigmask (SIGTIMER),
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[1 ... _SIGSET_NWORDS-1] = 0 }
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};
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/* Block all signals, including internal glibc ones. */
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static inline void
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__libc_signal_block_all (sigset_t *set)
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{
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INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_BLOCK, &sigall_set, set,
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_NSIG / 8);
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}
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/* Block all application signals (excluding internal glibc ones). */
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static inline void
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__libc_signal_block_app (sigset_t *set)
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{
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sigset_t allset = sigall_set;
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__clear_internal_signals (&allset);
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INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_BLOCK, &allset, set,
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_NSIG / 8);
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}
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/* Block only SIGTIMER and return the previous set on SET. */
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static inline void
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__libc_signal_block_sigtimer (sigset_t *set)
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{
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INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_BLOCK, &sigtimer_set, set,
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_NSIG / 8);
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}
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/* Unblock only SIGTIMER and return the previous set on SET. */
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static inline void
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__libc_signal_unblock_sigtimer (sigset_t *set)
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{
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INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_UNBLOCK, &sigtimer_set, set,
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_NSIG / 8);
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}
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/* Restore current process signal mask. */
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static inline void
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__libc_signal_restore_set (const sigset_t *set)
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{
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INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_SETMASK, set, NULL,
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_NSIG / 8);
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}
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/* Used to communicate with signal handler. */
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extern struct xid_command *__xidcmd attribute_hidden;
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#endif
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