acpid: blocked writes can lead to acpid daemon hang

acpid.c in acpid before 2.0.9 does not properly handle a situation in which a process has connected to acpid.socket but is not reading any data, which allows local users to cause a denial of service (daemon hang) via a crafted application that performs a connect system call but no read system calls.

samples/powerbtn/powerbtn.sh in acpid (aka acpid2) 2.0.16 and earlier uses the pidof program incorrectly, which allows local users to gain privileges by running a program with the name kded4 and a DBUS_SESSION_BUS_ADDRESS environment variable containing commands.

acpid: Unsafe umask for actions executed by acpid

event.c in acpid (aka acpid2) before 2.0.11 does not have an appropriate umask setting during execution of event-handler scripts, which might allow local users to (1) perform write operations within directories created by a script, or (2) read files created by a script, via standard filesystem system calls.