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app.c: make sure that no non-async-signal-safe syscalls are used after

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fork before exec

Posix does only allow async-signal-safe syscalls after fork before exec.
As asterisk ignores this, functions like TrySystem or System sometimes
end up in a deadlocked child process. The patch prevents the use of
non-async-signal-safe syscalls.

ASTERISK-28776

Change-Id: Idc76365c0592ee3f3b3bd72a4f48f7a098978e8e
This commit is contained in:
Pirmin Walthert
2020-04-14 18:02:19 +02:00
committed by George Joseph
parent 7fbfbe7da0
commit 6b2d945174
3 changed files with 75 additions and 58 deletions
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22
main/asterisk.c
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@@ -388,6 +388,10 @@ static int multi_thread_safe;
static char randompool[256];
#ifdef HAVE_CAP
static cap_t child_cap;
#endif
static int sig_alert_pipe[2] = { -1, -1 };
static struct {
unsigned int need_reload:1;
@@ -1099,13 +1103,7 @@ static pid_t safe_exec_prep(int dualfork)
if (pid == 0) {
#ifdef HAVE_CAP
cap_t cap = cap_from_text("cap_net_admin-eip");
if (cap_set_proc(cap)) {
/* Careful with order! Logging cannot happen after we close FDs */
ast_log(LOG_WARNING, "Unable to remove capabilities.\n");
}
cap_free(cap);
cap_set_proc(child_cap);
#endif
#ifdef HAVE_WORKING_FORK
if (ast_opt_high_priority) {
@@ -1804,10 +1802,8 @@ int ast_set_priority(int pri)
if (pri) {
sched.sched_priority = 10;
if (sched_setscheduler(0, SCHED_RR, &sched)) {
ast_log(LOG_WARNING, "Unable to set high priority\n");
return -1;
} else
ast_verb(1, "Set to realtime thread\n");
}
} else {
sched.sched_priority = 0;
/* According to the manpage, these parameters can never fail. */
@@ -3920,8 +3916,14 @@ int main(int argc, char *argv[])
exit(1);
}
#ifdef HAVE_CAP
child_cap = cap_from_text("cap_net_admin-eip");
#endif
/* Not a remote console? Start the daemon. */
asterisk_daemon(isroot, runuser, rungroup);
#ifdef HAS_CAP
cap_free(child_cap);
#endif
return 0;
}