Vigil@nce - Linux kernel: denial of service via EXT4_ORPHAN_FS
May 2013 by Vigil@nce
This bulletin was written by Vigil@nce : http://vigilance.fr/offer
SYNTHESIS OF THE VULNERABILITY
An attacker can mount an ext4 filesystem with no journal and using
an orphan extend, to create an infinite loop in the Linux kernel,
in order to trigger a denial of service.
Impacted products: Linux
Severity: 2/4
Creation date: 26/04/2013
DESCRIPTION OF THE VULNERABILITY
The ext4 filesystem uses the EXT4_ORPHAN_FS flag to indicate that
an "extend" is orphan.
The ext4_orphan_cleanup() function is called to fix the problem.
However, if there is no ext4 journal, the ext4_orphan_del()
function immediately returns, without removing the inode. The
function then indefinitely continues to process this inode.
An attacker can therefore mount an ext4 filesystem with no journal
and using an orphan extend, to create an infinite loop in the
Linux kernel, in order to trigger a denial of service.
ACCESS TO THE COMPLETE VIGIL@NCE BULLETIN
http://vigilance.fr/vulnerability/Linux-kernel-denial-of-service-via-EXT4-ORPHAN-FS-12719