The add_free_nid function in fs/f2fs/node.c in the Linux kernel before 4.12 does not properly track an allocated nid, which allows local users to cause a denial of service (race condition) or possibly have unspecified other impact via concurrent threads. Upstream patch: https://github.com/torvalds/linux/commit/30a61ddf8117c26ac5b295e1233eaa9629a94ca3
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1563517]
This was fixed for Fedora with the 4.12 kernel