A flaw was found in the implementation of the BTRFS file system code. An attacker who is able to mount (or convince someone to mount) a crafted BTRFS filesystem and performing common filesystem operations can possibly cause an out-of-bounds write to memory.
This could lead to memory corruption or possibly privilege escalation.
Created kernel tracking bugs for this issue:
Affects: fedora-all [bug 1784925]
As the BTRFS module will be auto-loaded when required, its use can be disabled by preventing the module from loading with the following instructions:
# echo "install btrfs /bin/true" >> /etc/modprobe.d/disable-btrfs.conf
The system will need to be restarted if the BTRFS modules are loaded, it may be possible to unload them. In most circumstances, the BTRFS kernel modules will be unable to be unloaded while any BTRFS filesystems are mounted or in use.
If the system requires this module to work correctly, this mitigation may not be suitable.
If you need further assistance, see KCS article https://access.redhat.com/solutions/41278 or contact Red Hat Global Support Services.
This flaw is rated as having Moderate impact, the attacker would require physical access to the system and also a local account to abuse the use-after-free.
This was fixed for Fedora with the 5.2 kernel rebases.