Bug 1402174 provided a way to allocate into different arenas. A concern is that an attacker can trigger an entire page's worth of data to be de-allocated, and eventually reused between partitions. This would allow bypassing the partition protection.

There is no useful data in a chunk by the time it's been recycled. The only risk would be in the face of UAF, is it what this is meant to guard against?

(In reply to Mike Hommey [:glandium] from comment #1) > There is no useful data in a chunk by the time it's been recycled. The only > risk would be in the face of UAF, is it what this is meant to guard against? Yea; one of the main goals of partitioning is to make exploiting UAFs more difficult; so reusing chunks between partitions would bring that back to the table.