Public bug reported:
Ubuntu version: Ubuntu 14.04.1 LTS
Package version: libnss-ldap_264-2.2ubuntu4
If a process using libnss-ldap calls fork() and SIGPIPE was blocked, the
atfork() handler in the child process failed to catch the SIGPIPE as it was
supposed to do, that is in the call to do_close_no_unbind(). So that, the
uncaught SIGPIPE will be eventually
delivered when the child unblocks signals. This usually make the child process
die unexpectedly.
I found a well-known Linux vendor fixed this issue with the following
patch. This unblocks the SIGPIPE before calling do_close_no_unbind() and
restores the original sigmask afterwards:
diff -up nss_ldap/ldap-nss.c nss_ldap/ldap-nss.c
--- nss_ldap/ldap-nss.c 2009-12-07 20:57:33.000000000 -0500
+++ nss_ldap/ldap-nss.c 2009-12-07 20:58:56.000000000 -0500
@@ -532,8 +532,13 @@
static void
do_atfork_child (void)
{
+ sigset_t unblock, mask;
debug ("==> do_atfork_child");
+ sigemptyset(&unblock);
+ sigaddset(&unblock, SIGPIPE);
+ sigprocmask(SIG_UNBLOCK, &unblock, &mask);
do_close_no_unbind ();
+ sigprocmask(SIG_SETMASK, &mask, NULL);
_nss_ldap_leave ();
debug ("<== do_atfork_child");
}
I'd like to see this patch applied.
** Affects: libnss-ldap (Ubuntu)
Importance: Undecided
Status: New
** Tags: atfork fork sigpipe
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https://bugs.launchpad.net/bugs/1397250
Title:
SIGPIPE not caught in do_atfork_child()
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