The f2fs implementation in the Linux kernel before 4.14 mishandles reference counts associated with f2fs_wait_discard_bios calls, which allows local users to cause a denial of service (BUG), as demonstrated by fstrim.
An upstream patch:
Created kernel tracking bugs for this issue:
Affects: fedora-all [bug 1550580]
This issue does not affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 5, 6, 7, its real-time kernel, Red Hat Enterprise MRG 2, Red Hat Enterprise Linux 7 for ARM 64 and Red Hat Enterprise Linux 7 for Power 9 LE, as the code with the flaw is not built and shipped in the products listed.
This was fixed in 4.14 rebases for all Fedora releases.