BASH PATCH REPORT ================= Bash-Release: 5.1 Patch-ID: bash51-012 Bug-Reported-by: Nikolay Borisov Bug-Reference-ID: <1a715205-06ce-413b-c1c0-2f5639ce06c0@suse.com> Bug-Reference-URL: https://lists.gnu.org/archive/html/bug-bash/2020-11/msg00091.html Bug-Description: There is a possible race condition that arises when a child process receives a signal trapped by the parent before it can reset the signal dispositions. The child process is not supposed to trap the signal in this circumstance. Patch (apply with `patch -p0'): *** ../bash-20201118/command.h 2020-08-14 15:04:39.000000000 -0400 --- command.h 2020-11-27 15:18:02.000000000 -0500 *************** *** 125,128 **** --- 125,129 ---- #define SUBSHELL_COPROC 0x40 /* subshell from a coproc pipeline */ #define SUBSHELL_RESETTRAP 0x80 /* subshell needs to reset trap strings on first call to trap */ + #define SUBSHELL_IGNTRAP 0x100 /* subshell should reset trapped signals from trap_handler */ /* A structure which represents a word. */ *** ../bash-20201118/execute_cmd.c 2020-11-23 14:16:48.000000000 -0500 --- execute_cmd.c 2020-11-27 16:43:25.000000000 -0500 *************** *** 1548,1551 **** --- 1548,1554 ---- reset_signal_handlers (); subshell_environment |= SUBSHELL_RESETTRAP; + /* Note that signal handlers have been reset, so we should no longer + reset the handler and resend trapped signals to ourselves. */ + subshell_environment &= ~SUBSHELL_IGNTRAP; /* We are in a subshell, so forget that we are running a trap handler or *************** *** 4321,4325 **** cmdflags |= CMD_NO_FORK; ! subshell_environment = SUBSHELL_FORK; /* XXX */ if (pipe_in != NO_PIPE || pipe_out != NO_PIPE) subshell_environment |= SUBSHELL_PIPE; --- 4324,4329 ---- cmdflags |= CMD_NO_FORK; ! /* We redo some of what make_child() does with SUBSHELL_IGNTRAP */ ! subshell_environment = SUBSHELL_FORK|SUBSHELL_IGNTRAP; /* XXX */ if (pipe_in != NO_PIPE || pipe_out != NO_PIPE) subshell_environment |= SUBSHELL_PIPE; *************** *** 4575,4578 **** --- 4580,4584 ---- reset_signal_handlers (); subshell_environment |= SUBSHELL_RESETTRAP; + subshell_environment &= ~SUBSHELL_IGNTRAP; if (async) *************** *** 5515,5518 **** --- 5521,5525 ---- /* Cancel traps, in trap.c. */ restore_original_signals (); + subshell_environment &= ~SUBSHELL_IGNTRAP; #if defined (JOB_CONTROL) *** ../bash-20201118/jobs.c 2020-08-04 10:17:39.000000000 -0400 --- jobs.c 2020-11-27 16:39:56.000000000 -0500 *************** *** 2218,2221 **** --- 2218,2223 ---- pid_t mypid; + subshell_environment |= SUBSHELL_IGNTRAP; + /* If this ends up being changed to modify or use `command' in the child process, go back and change callers who free `command' in diff -rC 2 ../bash-20201118/nojobs.c nojobs.c *** ../bash-20201118/nojobs.c 2020-07-08 10:11:25.000000000 -0400 --- nojobs.c 2020-11-27 16:38:36.000000000 -0500 *************** *** 576,579 **** --- 576,581 ---- #endif + subshell_environment |= SUBSHELL_IGNTRAP; + default_tty_job_signals (); } *** ../bash-20201118/sig.c 2020-11-23 13:22:17.000000000 -0500 --- sig.c 2020-11-28 10:21:43.000000000 -0500 *************** *** 56,60 **** #endif ! extern void initialize_siglist (); #if !defined (JOB_CONTROL) --- 56,61 ---- #endif ! extern void initialize_siglist PARAMS((void)); ! extern void set_original_signal PARAMS((int, SigHandler *)); #if !defined (JOB_CONTROL) *************** *** 256,259 **** --- 257,267 ---- XHANDLER(i) = oact.sa_handler; XSAFLAGS(i) = oact.sa_flags; + + #if 0 + set_original_signal (XSIG(i), XHANDLER(i)); /* optimization */ + #else + set_original_signal (XSIG(i), act.sa_handler); /* optimization */ + #endif + /* Don't do anything with signals that are ignored at shell entry if the shell is not interactive. */ *** ../bash-20201118/subst.c 2020-11-16 10:33:15.000000000 -0500 --- subst.c 2020-11-27 16:07:00.000000000 -0500 *************** *** 5952,5955 **** --- 5952,5956 ---- /* Cancel traps, in trap.c. */ restore_original_signals (); /* XXX - what about special builtins? bash-4.2 */ + subshell_environment &= ~SUBSHELL_IGNTRAP; QUIT; /* catch any interrupts we got post-fork */ setup_async_signals (); *************** *** 6383,6386 **** --- 6384,6388 ---- QUIT; /* catch any interrupts we got post-fork */ subshell_environment |= SUBSHELL_RESETTRAP; + subshell_environment &= ~SUBSHELL_IGNTRAP; } diff -rC 2 ../bash-20201118/trap.c trap.c *** ../bash-20201118/trap.c 2020-11-28 12:04:07.000000000 -0500 --- trap.c 2020-11-28 10:22:10.000000000 -0500 *************** *** 482,485 **** --- 482,511 ---- } + /* This means we're in a subshell, but have not yet reset the handler for + trapped signals. We're not supposed to execute the trap in this situation; + we should restore the original signal and resend the signal to ourselves + to preserve the Posix "signal traps that are not being ignored shall be + set to the default action" semantics. */ + if ((subshell_environment & SUBSHELL_IGNTRAP) && trap_list[sig] != (char *)IGNORE_SIG) + { + sigset_t mask; + + /* Paranoia */ + if (original_signals[sig] == IMPOSSIBLE_TRAP_HANDLER) + original_signals[sig] = SIG_DFL; + + restore_signal (sig); + + /* Make sure we let the signal we just caught through */ + sigemptyset (&mask); + sigprocmask (SIG_SETMASK, (sigset_t *)NULL, &mask); + sigdelset (&mask, sig); + sigprocmask (SIG_SETMASK, &mask, (sigset_t *)NULL); + + kill (getpid (), sig); + + SIGRETURN (0); + } + if ((sig >= NSIG) || (trap_list[sig] == (char *)DEFAULT_SIG) || *** ../bash-5.1/patchlevel.h 2020-06-22 14:51:03.000000000 -0400 --- patchlevel.h 2020-10-01 11:01:28.000000000 -0400 *************** *** 26,30 **** looks for to find the patch level (for the sccs version string). */ ! #define PATCHLEVEL 11 #endif /* _PATCHLEVEL_H_ */ --- 26,30 ---- looks for to find the patch level (for the sccs version string). */ ! #define PATCHLEVEL 12 #endif /* _PATCHLEVEL_H_ */