Currently (portage-2.1_pre6-r5), portage's buildpkg logic creates a binary package in /var/tmp/portage, and then uses `mv` to move it to the package dir. On SELinux systems, this will cause one of two problems: either the resulting package will be labeled incorrectly as a portage temporary file, or sandbox violations will occur as mv tries to write to /proc/self/attr/fscreate in order to create the destination file with the original context. Possible solutions were discussed in #gentoo-portage, including using the existing Python code for moving files in SELinux. The desired result, though, is that the package after moving to $PKGDIR has the same label as $PKGDIR itself.
Created attachment 82986 [details, diff] patch to create tbz2 directly in ${PKGDIR}/All Please test this patch which creates the tbz2 package directly in ${PKGDIR}/All so that it will hopefully get the proper label automatically. As an added benefit, it avoids the intermediate temporary file, for better efficiency. This is in svn r2986.
Created attachment 82987 [details, diff] patch to create tbz2 directly in ${PKGDIR}/All This patch applies cleanly against 2.1_pre6-r6.
Released in 2.1_pre6-r7. Thanks for reporting.