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BASH PATCH REPORT
=================
Bash-Release: 5.1
Patch-ID: bash51-012
Bug-Reported-by: Nikolay Borisov <nborisov@suse.com>
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_ */
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