In the Linux kernel through 4.14.13, drivers/block/loop.c mishandles lo_release serialization, which allows attackers to cause a denial of service (__lock_acquire use-after-free) or possibly have unspecified other impact.
https://usn.ubuntu.com/3632-1/
https://usn.ubuntu.com/3619-2/
https://usn.ubuntu.com/3619-1/
https://usn.ubuntu.com/3617-3/
https://usn.ubuntu.com/3617-2/
https://usn.ubuntu.com/3617-1/
https://usn.ubuntu.com/3583-2/
https://usn.ubuntu.com/3583-1/
https://github.com/torvalds/linux/commit/ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5
https://access.redhat.com/errata/RHSA-2018:3096
https://access.redhat.com/errata/RHSA-2018:3083
https://access.redhat.com/errata/RHSA-2018:2948