A flaw was found in Linux kernel in the ext4 filesystem code. A use-after-free is possible in ext4_ext_remove_space() function when mounting and operating a crafted ext4 image.
https://usn.ubuntu.com/3871-5/
https://usn.ubuntu.com/3871-4/
https://usn.ubuntu.com/3871-3/
https://usn.ubuntu.com/3871-1/
https://usn.ubuntu.com/3753-2/
https://usn.ubuntu.com/3753-1/
https://lists.debian.org/debian-lts-announce/2018/07/msg00020.html