Whenever I use patch, it resets the contexts of all the files it touches to user_u:object_r:tmp_t:s0. I'm using it by applying a diff from stdin, if that makes a difference. This is particularly difficult since it resets the contexts even when you're a non-root user, but restorecon is only in root's path.
Oh, by the way, I think patch in more recent versions of Fedora doesn't do this--it's only been happening to me in RHEL 5 (and in RHEL 4 before that).
*** This bug has been marked as a duplicate of 229329 ***