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NOFORK fixes

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"rm -i FILE" and "yes" can now be interrupted by ^C in hush.
This also now works:

$ usleep 19999999
^C
$ echo $?
130

function                                             old     new   delta
run_pipe                                            1668    1711     +43
pseudo_exec_argv                                     312     321      +9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 52/0)               Total: 52 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-08-02 16:37:39 +02:00
parent 95f7953f2c
commit 7c40ddd950
6 changed files with 48 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
coreutils/rm.c
View File

@ -16,7 +16,8 @@
//config: help
//config: rm is used to remove files or directories.
//applet:IF_RM(APPLET_NOFORK(rm, rm, BB_DIR_BIN, BB_SUID_DROP, rm))
//applet:IF_RM(APPLET_NOEXEC(rm, rm, BB_DIR_BIN, BB_SUID_DROP, rm))
/* was NOFORK, but then "rm -i FILE" can't be ^C'ed if run by hush */
//kbuild:lib-$(CONFIG_RM) += rm.o
@ -36,7 +37,7 @@
#include "libbb.h"
/* This is a NOFORK applet. Be very careful! */
/* This is a NOEXEC applet. Be very careful! */
int rm_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int rm_main(int argc UNUSED_PARAM, char **argv)

5
coreutils/seq.c
View File

@ -12,7 +12,8 @@
//config: help
//config: print a sequence of numbers
//applet:IF_SEQ(APPLET_NOFORK(seq, seq, BB_DIR_USR_BIN, BB_SUID_DROP, seq))
//applet:IF_SEQ(APPLET_NOEXEC(seq, seq, BB_DIR_USR_BIN, BB_SUID_DROP, seq))
/* was NOFORK, but then "seq 1 999999999" can't be ^C'ed if run by hush */
//kbuild:lib-$(CONFIG_SEQ) += seq.o
@ -26,7 +27,7 @@
#include "libbb.h"
/* This is a NOFORK applet. Be very careful! */
/* This is a NOEXEC applet. Be very careful! */
int seq_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int seq_main(int argc, char **argv)

7
coreutils/usleep.c
View File

@ -38,6 +38,13 @@ int usleep_main(int argc UNUSED_PARAM, char **argv)
bb_show_usage();
}
/* Safe wrt NOFORK? (noforks are not allowed to run for
* a long time). Try "usleep 99999999" + ^C + "echo $?"
* in hush with FEATURE_SH_NOFORK=y.
* At least on uclibc, usleep() thanslates to nanosleep()
* which returns early on any signal (even caught one),
* and uclibc does not loop back on EINTR.
*/
usleep(xatou(argv[1]));
return EXIT_SUCCESS;

3
coreutils/yes.c
View File

@ -17,7 +17,8 @@
//config: yes is used to repeatedly output a specific string, or
//config: the default string 'y'.
//applet:IF_YES(APPLET_NOFORK(yes, yes, BB_DIR_USR_BIN, BB_SUID_DROP, yes))
//applet:IF_YES(APPLET_NOEXEC(yes, yes, BB_DIR_USR_BIN, BB_SUID_DROP, yes))
/* was NOFORK, but then yes can't be ^C'ed if run by hush */
//kbuild:lib-$(CONFIG_YES) += yes.o

3
docs/nofork_noexec.txt
View File

@ -52,6 +52,9 @@ xargs, find, shells do it (grep for "spawn_and_wait" and
This poses much more serious limitations on what applet can do:
* all NOEXEC limitations apply.
* do not run for a long time or wait for user input:
hush shell only handles signals (like ^C) after you return
from APPLET_main().
* do not ever exit() or exec().
- xfuncs are okay. They are using special trick to return
to the caller applet instead of dying when they detect "x" condition.

31
shell/hush.c
View File

@ -7363,6 +7363,8 @@ static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save,
*/
close_saved_fds_and_FILE_fds();
//FIXME: should also close saved redir fds
/* Without this, "rm -i FILE" can't be ^C'ed: */
switch_off_special_sigs(G.special_sig_mask);
debug_printf_exec("running applet '%s'\n", argv[0]);
run_applet_no_and_exit(a, argv[0], argv);
}
@ -8045,6 +8047,24 @@ static NOINLINE int run_pipe(struct pipe *pi)
add_vars(old_vars);
/* clean_up_and_ret0: */
restore_redirects(squirrel);
/*
* Try "usleep 99999999" + ^C + "echo $?"
* with FEATURE_SH_NOFORK=y.
*/
if (!funcp) {
/* It was builtin or nofork.
* if this would be a real fork/execed program,
* it should have died if a fatal sig was received.
* But OTOH, there was no separate process,
* the sig was sent to _shell_, not to non-existing
* child.
* Let's just handle ^C only, this one is obvious:
* we aren't ok with exitcode 0 when ^C was pressed
* during builtin/nofork.
*/
if (sigismember(&G.pending_set, SIGINT))
rcode = 128 + SIGINT;
}
clean_up_and_ret1:
free(argv_expanded);
IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
@ -8060,6 +8080,14 @@ static NOINLINE int run_pipe(struct pipe *pi)
if (rcode == 0) {
debug_printf_exec(": run_nofork_applet '%s' '%s'...\n",
argv_expanded[0], argv_expanded[1]);
/*
* Note: signals (^C) can't interrupt here.
* We remember them and they will be acted upon
* after applet returns.
* This makes applets which can run for a long time
* and/or wait for user input ineligible for NOFORK:
* for example, "yes" or "rm" (rm -i waits for input).
*/
rcode = run_nofork_applet(n, argv_expanded);
}
goto clean_up_and_ret;
@ -8491,7 +8519,7 @@ static int run_list(struct pipe *pi)
G.last_bg_pid = pi->cmds[pi->num_cmds - 1].pid;
G.last_bg_pid_exitcode = 0;
debug_printf_exec(": cmd&: exitcode EXIT_SUCCESS\n");
/* Check pi->pi_inverted? "! sleep 1 & echo $?": bash says 1. dash and ash says 0 */
/* Check pi->pi_inverted? "! sleep 1 & echo $?": bash says 1. dash and ash say 0 */
rcode = EXIT_SUCCESS;
goto check_traps;
} else {
@ -10178,6 +10206,7 @@ static int wait_for_child_or_signal(struct pipe *waitfor_pipe, pid_t waitfor_pid
/* So, did we get a signal? */
sig = check_and_run_traps();
if (sig /*&& sig != SIGCHLD - always true */) {
/* Do this for any (non-ignored) signal, not only for ^C */
ret = 128 + sig;
break;
}