Hmm, there are two possible candidates in the init.d script for the RHEL 6 package of an older version of squid (doesn't look like bug submitter is using a current version).
In stop():
rm -rf $SQUID_PIDFILE_DIR/*
and in restart():
rm -rf $SQUID_PIDFILE_DIR/*
SQUID_PIDFILE_DIR is hardcoded to "/var/run/squid" at the top of my copy of the init script. But, neither of those rm commands check first to make sure that SQUID_PIDFILE_DIR isn't empty (or, better yet, is in /var and doesn't contain ".."), and either the submitter's copy of the script is mangled or something else somewhere is stomping on SQUID_PIDFILE_DIR in the shell environment.
squid-3.1.10-29.el6.src.rpm (from ftp.redhat.com, buried where they keep SRPMs) has squid.init within, and that file has no mention of SQUID_PIDFILE_DIR. A few other spot-checked versions are the same way.
I guess they applied that change which was obviously written against a very different init script where the variable is actually defined, got QA to test it and immediately backed it out.
That would be my guess too, although the package maintainer confirmed it on (presumably) a fresh install. I can't find a candidate rm command anywhere in the SRPM, so maybe an upstream file got merged into distrib somehow? I don't have access to an RHEL system to try it out, and can't find the distrib RPM yet to check.
In stop():
and in restart(): SQUID_PIDFILE_DIR is hardcoded to "/var/run/squid" at the top of my copy of the init script. But, neither of those rm commands check first to make sure that SQUID_PIDFILE_DIR isn't empty (or, better yet, is in /var and doesn't contain ".."), and either the submitter's copy of the script is mangled or something else somewhere is stomping on SQUID_PIDFILE_DIR in the shell environment....I should grep my init scripts for "rm".