Description of problem:

SSSD components comunicate using a low-level DBus protocol. On initializing the
server dbus is given a filename that represents a known interface and creates
the socket When server shuts down, it calls a dbus cleanup function which
removes the socket.

Normally, this is OK, problem arise when:

1. a sssd component (a back end for example) is stopped
2. monitor detects it does not respond, kills it and spawns a new one
3. the old back end calls its shutdown function /after/ the new one has started
4. dbus removes the named socket

Version-Release number of selected component (if applicable):

sssd-1.5.1-53

How reproducible:

always

Steps to Reproduce:

1. start sssd
2. killall -STOP sssd_be
3. wait until monitor sends TERM to sssd_be and spawns a new one
4. killall -CONT sssd_be
5. getent passwd foobar

Actual results:

the socket /var/lib/sss/pipes/private/sbus-dp_$domain is removed
sssd_nss crashes

Expected results:

sssd only reconnects to the new back end, the old back end shuts down
gracefully

Additional info:

The crash was found by Kaushik Banerjee