https://bugs.freedesktop.org/show_bug.cgi?id=82162
--- Comment #3 from Michel Dänzer michel@daenzer.net --- Looks like the Mesa radeonsi driver tries to allocate buffer objects of zero bytes size, which isn't allowed.
Since nobody else has reported this, I wonder if your driver binaries got corrupted somehow. Does uninstalling the PPA and installing it again help?