pcre compiled context files invalid with pcre updates?

[Sven Vermeulen <sven.vermeulen@siphos.be>]

Hi all,

In Gentoo, we notice some unexpected behavior with the compiled
file_contexts files after upgrading (lib)pcre:

https://bugs.gentoo.org/show_bug.cgi?id=516608

I think what is happening is that the pcre data, which is built with one
pcre version, is not (fully) compatible with a more recent pcre version. In
the changelog of pcre I find type changes of (internal or not) variables by
pcre.

If this assumption is correct, perhaps we should store the pcre version used
to build the *.bin files in the file itself. Right now we store a magic (to
make sure it is a compiled file_contexts file) and a version specific for
libselinux, but not a version specific for PCRE.

The pcre header defines PCRE_MAJOR and PCRE_MINOR which we can use.

Do you think the above analysis makes sense? The bug linked earlier on has a
gdb backtrace for those interested. Any other pointers that might help us
troubleshoot this would be appreciated.

Wkr,
	Sven Vermeulen