drivers/infiniband/core/ucma.c in the Linux kernel through 4.17.11 allows ucma_leave_multicast to access a certain data structure after a cleanup step in ucma_process_join, which allows attackers to cause a denial of service (use-after-free).
git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=cb2595c1393b4a5211534e6f0a0fbad369e21ad8
access.redhat.com/errata/RHSA-2019:0831
access.redhat.com/errata/RHSA-2019:2029
access.redhat.com/errata/RHSA-2019:2043
github.com/torvalds/linux/commit/cb2595c1393b4a5211534e6f0a0fbad369e21ad8
lists.debian.org/debian-lts-announce/2018/10/msg00003.html
usn.ubuntu.com/3797-1/
usn.ubuntu.com/3797-2/
usn.ubuntu.com/3847-1/
usn.ubuntu.com/3847-2/
usn.ubuntu.com/3847-3/
usn.ubuntu.com/3849-1/
usn.ubuntu.com/3849-2/
www.debian.org/security/2018/dsa-4308