From 15409324f1974d41c183904ad575da7188058c1c Mon Sep 17 00:00:00 2001
From: Chet Ramey <chet.ramey@case.edu>
Date: Wed, 17 Nov 2021 16:47:24 -0500
Subject: [PATCH] Bash-5.1 patch 12: fix race condition with child processes
and resetting trapped signals
---
command.h | 1 +
execute_cmd.c | 8 +++++++-
jobs.c | 2 ++
nojobs.c | 2 ++
patchlevel.h | 2 +-
sig.c | 10 +++++++++-
subst.c | 2 ++
trap.c | 26 ++++++++++++++++++++++++++
8 files changed, 50 insertions(+), 3 deletions(-)
diff --git a/command.h b/command.h
index 914198f9..b8477528 100644
--- a/command.h
+++ b/command.h
@@ -124,6 +124,7 @@ enum command_type { cm_for, cm_case, cm_while, cm_if, cm_simple, cm_select,
#define SUBSHELL_PROCSUB 0x20 /* subshell caused by <(command) or >(command) */
#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. */
typedef struct word_desc {
diff --git a/execute_cmd.c b/execute_cmd.c
index 90129e06..425679a2 100644
--- a/execute_cmd.c
+++ b/execute_cmd.c
@@ -1547,6 +1547,9 @@ execute_in_subshell (command, asynchronous, pipe_in, pipe_out, fds_to_close)
clear_pending_traps ();
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
that the signal handler has changed (we haven't changed it!) */
@@ -4320,7 +4323,8 @@ execute_simple_command (simple_command, pipe_in, pipe_out, async, fds_to_close)
already_forked = 1;
cmdflags |= CMD_NO_FORK;
- subshell_environment = SUBSHELL_FORK; /* XXX */
+ /* 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;
if (async)
@@ -4574,6 +4578,7 @@ run_builtin:
trap strings if we run trap to change a signal disposition. */
reset_signal_handlers ();
subshell_environment |= SUBSHELL_RESETTRAP;
+ subshell_environment &= ~SUBSHELL_IGNTRAP;
if (async)
{
@@ -5514,6 +5519,7 @@ execute_disk_command (words, redirects, command_line, pipe_in, pipe_out,
reset_terminating_signals (); /* XXX */
/* Cancel traps, in trap.c. */
restore_original_signals ();
+ subshell_environment &= ~SUBSHELL_IGNTRAP;
#if defined (JOB_CONTROL)
FREE (p);
diff --git a/jobs.c b/jobs.c
index a581f305..7c3b6e83 100644
--- a/jobs.c
+++ b/jobs.c
@@ -2217,6 +2217,8 @@ make_child (command, flags)
signals to the default state for a new process. */
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
the child process when this returns. */
diff --git a/nojobs.c b/nojobs.c
index c5fc83d9..f2563ca0 100644
--- a/nojobs.c
+++ b/nojobs.c
@@ -575,6 +575,8 @@ make_child (command, flags)
last_asynchronous_pid = getpid ();
#endif
+ subshell_environment |= SUBSHELL_IGNTRAP;
+
default_tty_job_signals ();
}
else
diff --git a/patchlevel.h b/patchlevel.h
index 8b14f289..eb2aca52 100644
--- a/patchlevel.h
+++ b/patchlevel.h
@@ -25,6 +25,6 @@
regexp `^#define[ ]*PATCHLEVEL', since that's what support/mkversion.sh
looks for to find the patch level (for the sccs version string). */
-#define PATCHLEVEL 11
+#define PATCHLEVEL 12
#endif /* _PATCHLEVEL_H_ */
diff --git a/sig.c b/sig.c
index 6964d862..e6537d26 100644
--- a/sig.c
+++ b/sig.c
@@ -55,7 +55,8 @@
# include "bashhist.h"
#endif
-extern void initialize_siglist ();
+extern void initialize_siglist PARAMS((void));
+extern void set_original_signal PARAMS((int, SigHandler *));
#if !defined (JOB_CONTROL)
extern void initialize_job_signals PARAMS((void));
@@ -255,6 +256,13 @@ initialize_terminating_signals ()
sigaction (XSIG (i), &act, &oact);
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. */
/* XXX - should we do this for interactive shells, too? */
diff --git a/subst.c b/subst.c
index 462752de..327de083 100644
--- a/subst.c
+++ b/subst.c
@@ -5951,6 +5951,7 @@ process_substitute (string, open_for_read_in_child)
free_pushed_string_input ();
/* 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 ();
#if 0
@@ -6382,6 +6383,7 @@ command_substitute (string, quoted, flags)
}
QUIT; /* catch any interrupts we got post-fork */
subshell_environment |= SUBSHELL_RESETTRAP;
+ subshell_environment &= ~SUBSHELL_IGNTRAP;
}
#if defined (JOB_CONTROL)
diff --git a/trap.c b/trap.c
index c7f8ded5..1b27fb3a 100644
--- a/trap.c
+++ b/trap.c
@@ -481,6 +481,32 @@ trap_handler (sig)
SIGRETURN (0);
}
+ /* 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) ||
(trap_list[sig] == (char *)IGNORE_SIG))
--
2.31.1