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authorDenys Vlasenko <vda.linux@googlemail.com>2020-02-18 16:46:01 +0100
committerDenys Vlasenko <vda.linux@googlemail.com>2020-02-18 16:46:01 +0100
commit23bc562a0556d1c0ddad4252fa8d46c863b5fa88 (patch)
tree3ad95cdddd273d569f55c57dcb6fe8f6ae488d51 /shell
parent47eb979404735b9528538968cb5eaac7355a0c5a (diff)
downloadbusybox-23bc562a0556d1c0ddad4252fa8d46c863b5fa88.tar.gz
ash,hush: add comment about masked SIGCHLD, handle SIG_IGNed SIGHUP as in bash
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'shell')
-rw-r--r--shell/ash.c26
-rw-r--r--shell/hush.c20
2 files changed, 37 insertions, 9 deletions
diff --git a/shell/ash.c b/shell/ash.c
index ff594050c..fea4b10a7 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -4307,8 +4307,19 @@ wait_block_or_sig(int *status)
#if 1
sigfillset(&mask);
sigprocmask2(SIG_SETMASK, &mask); /* mask is updated */
- while (!got_sigchld && !pending_sig)
+ while (!got_sigchld && !pending_sig) {
sigsuspend(&mask);
+ /* ^^^ add "sigdelset(&mask, SIGCHLD);" before sigsuspend
+ * to make sure SIGCHLD is not masked off?
+ * It was reported that this:
+ * fn() { : | return; }
+ * shopt -s lastpipe
+ * fn
+ * exec ash SCRIPT
+ * under bash 4.4.23 runs SCRIPT with SIGCHLD masked,
+ * making "wait" commands in SCRIPT block forever.
+ */
+ }
sigprocmask(SIG_SETMASK, &mask, NULL);
#else /* unsafe: a signal can set pending_sig after check, but before pause() */
while (!got_sigchld && !pending_sig)
@@ -14170,11 +14181,6 @@ init(void)
sigmode[SIGCHLD - 1] = S_DFL; /* ensure we install handler even if it is SIG_IGNed */
setsignal(SIGCHLD);
- /* bash re-enables SIGHUP which is SIG_IGNed on entry.
- * Try: "trap '' HUP; bash; echo RET" and type "kill -HUP $$"
- */
- signal(SIGHUP, SIG_DFL);
-
{
char **envp;
const char *p;
@@ -14512,6 +14518,14 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
}
#endif
state4: /* XXX ??? - why isn't this before the "if" statement */
+
+ /* Interactive bash re-enables SIGHUP which is SIG_IGNed on entry.
+ * Try:
+ * trap '' hup; bash; echo RET # type "kill -hup $$", see SIGHUP having effect
+ * trap '' hup; bash -c 'kill -hup $$; echo ALIVE' # here SIGHUP is SIG_IGNed
+ */
+ signal(SIGHUP, SIG_DFL);
+
cmdloop(1);
}
#if PROFILE
diff --git a/shell/hush.c b/shell/hush.c
index 6e44d4e11..bced388bf 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -9775,10 +9775,14 @@ static void install_sighandlers(unsigned mask)
*/
if (sig == SIGCHLD)
continue;
- /* bash re-enables SIGHUP which is SIG_IGNed on entry.
- * Try: "trap '' HUP; bash; echo RET" and type "kill -HUP $$"
+ /* Interactive bash re-enables SIGHUP which is SIG_IGNed on entry.
+ * Try:
+ * trap '' hup; bash; echo RET # type "kill -hup $$", see SIGHUP having effect
+ * trap '' hup; bash -c 'kill -hup $$; echo ALIVE' # here SIGHUP is SIG_IGNed
*/
- //if (sig == SIGHUP) continue; - TODO?
+ if (sig == SIGHUP && G_interactive_fd)
+ continue;
+ /* Unless one of the above signals, is it SIG_IGN? */
if (old_handler == SIG_IGN) {
/* oops... restore back to IGN, and record this fact */
install_sighandler(sig, old_handler);
@@ -11554,6 +11558,16 @@ static int wait_for_child_or_signal(struct pipe *waitfor_pipe, pid_t waitfor_pid
/* It is vitally important for sigsuspend that SIGCHLD has non-DFL handler! */
/* Note: sigsuspend invokes signal handler */
sigsuspend(&oldset);
+ /* ^^^ add "sigdelset(&oldset, SIGCHLD)" before sigsuspend
+ * to make sure SIGCHLD is not masked off?
+ * It was reported that this:
+ * fn() { : | return; }
+ * shopt -s lastpipe
+ * fn
+ * exec hush SCRIPT
+ * under bash 4.4.23 runs SCRIPT with SIGCHLD masked,
+ * making "wait" commands in SCRIPT block forever.
+ */
restore:
sigprocmask(SIG_SETMASK, &oldset, NULL);
check_sig: