A user with permissions to mount and unmount a crafted ext4 file system, via any transport mechanism (local, USB, ISCSI) can lead to a use-after-free when attempting to delete a directory after the disk has been umounted.
This can lead to possible memory corruption and privilege escalation.
Created kernel tracking bugs for this issue:
Affects: fedora-all [bug 1781680]
Ext4 filesytems are built into the kernel so it is not possible to prevent the kernel module from loading. However, this flaw can be prevented by disallowing mounting of untrusted filesystems.
As mounting is a privileged operation, (except for device hotplug) removing the ability for mounting and unmounting will prevent this flaw from being exploited.
This issue has been addressed in the following products:
Red Hat Enterprise Linux 7
Via RHSA-2020:2104 https://access.redhat.com/errata/RHSA-2020:2104
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):
This was fixed for Fedora in the 5.4.4 stable kernel update.