klogd: fix the problem of delayed handling of ^C and SIGTERM

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 30 insertions, 1 deletions

diff --git a/sysklogd/klogd.c b/sysklogd/klogd.c
index 0d4c2578d..db32065fb 100644
--- a/sysklogd/klogd.c
+++ b/sysklogd/klogd.c
@@ -150,12 +150,41 @@ int klogd_main(int argc UNUSED_PARAM, char **argv)
          */
         klogd_open();
         openlog("kernel", 0, LOG_KERN);
+        /*
+         * glibc problem: for some reason, glibc changes LOG_KERN to LOG_USER
+         * above. The logic behind this is that standard
+         * http://pubs.opengroup.org/onlinepubs/9699919799/functions/syslog.html
+         * says the following about openlog and syslog:
+         * "LOG_USER
+         *  Messages generated by arbitrary processes.
+         *  This is the default facility identifier if none is specified."
+         *
+         * I believe glibc misinterpreted this text as "if openlog's
+         * third parameter is 0 (=LOG_KERN), treat it as LOG_USER".
+         * Whereas it was meant to say "if *syslog* is called with facility
+         * 0 in its 1st parameter without prior call to openlog, then perform
+         * implicit openlog(LOG_USER)".
+         *
+         * As a result of this, eh, feature, standard klogd was forced
+         * to open-code its own openlog and syslog implementation (!).
+         *
+         * Note that prohibiting openlog(LOG_KERN) on libc level does not
+         * add any security: any process can open a socket to "/dev/log"
+         * and write a string "<0>Voila, a LOG_KERN + LOG_EMERG message"
+         *
+         * Google code search tells me there is no widespread use of
+         * openlog("foo", 0, 0), thus fixing glibc won't break userspace.
+         *
+         * The bug against glibc was filed:
+         * bugzilla.redhat.com/show_bug.cgi?id=547000
+         */
 
         if (i)
                 klogd_setloglevel(i);
 
-        bb_signals(BB_FATAL_SIGS, record_signo);
         signal(SIGHUP, SIG_IGN);
+        /* We want klogd_read to not be restarted, thus _norestart: */
+        bb_signals_recursive_norestart(BB_FATAL_SIGS, record_signo);
 
         syslog(LOG_NOTICE, "klogd started: %s", bb_banner);