Description:
------------
See downstream bug report:

https://bugzilla.redhat.com/show_bug.cgi?id=1398474

SELinux blocks web servers from what it calls 'execmem' actions by default; as I understand it, this means execution of writeable memory, which is considered a potential avenue for exploitation and not to be necessary for well-written code.

With PHP 7.0.13's default configuration, where just-in-time compilation of PCREs is enabled, Fedora 25 systems see a flood of these 'execmem' denials. Disabling the PCRE JIT feature with `pcre.jit=0` makes them go away.

There is some more discussion of this at https://unix.stackexchange.com/questions/287831/how-to-work-out-why-apache-is-attempting-execmem , where several people traced this problem to the PCRE JIT code using gdb and backtraces are available. These seem to run through _pcre_jit_compile / pcre_study / pcre_get_compiled_regex_cache / php_do_pcre_match .