rtld: Sync 5/7 - Fix fd leak with parallel dlopen and fork
Rtld did not set FD_CLOEXEC on its internal file descriptors; therefore,
such a file descriptor may be passed to a process created by another
thread running in parallel to dlopen() or fdlopen().
No other threads are expected to be running during parsing of the hints
and libmap files but the file descriptors need not be passed to child
processes so add O_CLOEXEC there as well.
As the F_DUPFD_CLOEXEC support was added in the kernel today, rtld
will temporarily fall back to separate dup/cloexec commands if
F_DUPFD_CLOEXEC fails. This fallback should be removed before
3.6 branches.
Taken from:
FreeBSD SVN 242587 (04 NOV 2012)