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Trap segfaults caused by service callbacks in separate process context

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This patch traps segfaults caused by 3rd party service callbacks in a
separate process context.  Effectively preventing a single programming
mistake from taking down the entire system.  Previously it was up to the
callback coder to write error free code so that PID 1 did not crash.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
This commit is contained in:
Joachim Nilsson
2015-02-16 10:21:03 +01:00
parent d6efe85a57
commit b4b63d3722
2 changed files with 46 additions and 3 deletions
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sig.c
+13 -1
View File
@@ -49,7 +49,7 @@
static int stopped = 0;
static uev_t sigint_watcher, sigpwr_watcher;
static uev_t sigchld_watcher;
static uev_t sigchld_watcher, sigsegv_watcher;
static uev_t sigstop_watcher, sigtstp_watcher, sigcont_watcher;
@@ -103,6 +103,15 @@ static void sigchld_cb(uev_ctx_t *UNUSED(ctx), uev_t *UNUSED(w), void *UNUSED(ar
svc_monitor(waitpid(-1, NULL, WNOHANG));
}
/*
* SIGSEGV: mostly if service callbacks segfault
*/
static void sigsegv_cb(uev_ctx_t *UNUSED(ctx), uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
{
_e("PID %d caused a segfault!\n", getpid());
exit(-1);
}
/*
* SIGSTOP/SIGTSTP: Paused by user or netflash
*/
@@ -204,6 +213,9 @@ void sig_setup(uev_ctx_t *ctx)
/* After initial bootstrap of Finit we call the service monitor to reap children */
uev_signal_init(ctx, &sigchld_watcher, sigchld_cb, NULL, SIGCHLD);
/* Trap SIGSEGV in case service callbacks crash */
uev_signal_init(ctx, &sigsegv_watcher, sigsegv_cb, NULL, SIGSEGV);
/* Stopping init is a bit tricky. */
uev_signal_init(ctx, &sigstop_watcher, sigstop_cb, NULL, SIGSTOP);
uev_signal_init(ctx, &sigtstp_watcher, sigstop_cb, NULL, SIGTSTP);
svc.c
+33 -2
View File
@@ -395,8 +395,39 @@ svc_cmd_t svc_enabled(svc_t *svc, int event, void *arg)
return SVC_STOP;
/* Is there a service plugin registered? */
if (svc->cb)
return svc->cb(svc, event, arg);
if (svc->cb) {
int status;
pid_t pid;
/* Let callback run in separate process so it doesn't crash PID 1 */
pid = fork();
if (-1 == pid) {
_pe("Failed in %s callback", svc->cmd);
return SVC_STOP;
}
if (!pid) {
status = svc->cb(svc, event, arg);
exit(status);
}
if (waitpid(pid, &status, 0) == -1) {
_pe("Failed reading status from %s callback", svc->cmd);
return SVC_STOP;
}
/* Callback normally exits here. */
if (WIFEXITED(status))
return WEXITSTATUS(status);
/* Check for SEGFAULT or other error ... */
if (WCOREDUMP(status))
_e("Callback to %s crashed!\n", svc->cmd);
else
_e("Callback to %s did not exit normally!\n", svc->cmd);
return SVC_STOP;
}
/* No service plugin, default to start, since listed in finit.conf */
return SVC_START;