The ext4_fill_super function in fs/ext4/super.c in the Linux kernel through 4.9.8 does not properly validate meta block groups, which allows physically proximate attackers to cause a denial of service (out-of-bounds read and system crash) via a crafted ext4 image.
https://access.redhat.com/errata/RHSA-2017:1297
https://access.redhat.com/errata/RHSA-2017:1298
https://access.redhat.com/errata/RHSA-2017:1308
https://bugzilla.redhat.com/show_bug.cgi?id=1395190
http://seclists.org/fulldisclosure/2016/Nov/75
https://github.com/torvalds/linux/commit/3a4b77cd47bb837b8557595ec7425f281f2ca1fe
https://lists.debian.org/debian-lts-announce/2017/12/msg00004.html