The ext4_fill_super function in fs/ext4/super.c in the Linux kernel through 4.15.15 does not always initialize the crc32c checksum driver, which allows attackers to cause a denial of service (ext4_xattr_inode_hash NULL pointer dereference and system crash) via a crafted ext4 image.
openwall.com/lists/oss-security/2018/03/29/1
access.redhat.com/errata/RHSA-2018:2948
access.redhat.com/errata/RHSA-2018:3083
access.redhat.com/errata/RHSA-2018:3096
bugzilla.kernel.org/show_bug.cgi?id=199183
bugzilla.redhat.com/show_bug.cgi?id=1560788
git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?id=18db4b4e6fc31eda838dd1c1296d67dbcb3dc957
git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?id=a45403b51582a87872927a3e0fc0a389c26867f1
usn.ubuntu.com/3695-1/
usn.ubuntu.com/3695-2/