Vigil@nce: Linux kernel, privilege elevation via eCryptfs
October 2009 by Vigil@nce
A local attacker can create a hard link on an eCryptfs file
system, in order to generate a denial of service, or to execute
code.
– Severity: 2/4
– Consequences: administrator access/rights, denial of service of
computer
– Provenance: user shell
– Means of attack: 1 attack
– Ability of attacker: technician (2/4)
– Confidence: confirmed by the editor (5/5)
– Diffusion of the vulnerable configuration: high (3/3)
– Creation date: 07/10/2009
IMPACTED PRODUCTS
– Linux kernel
DESCRIPTION OF THE VULNERABILITY
The Linux kernel supports the eCryptfs file system since version
2.6.19.
A file can have several hard links, which are different access
path to the same file.
When:
– a file is stored on an eCryptfs file system, and
– two hard links are available for this file, and
– the file is opened, and
– all links are removed, and
– a read() or write() is done on the previously opened file,
then, a NULL pointer is dereferenced in ecryptfs_read_update_atime()
(access time update). This error stops the kernel.
A local attacker can thus create a hard link on an eCryptfs file
system, in order to generate a denial of service.
An attacker can also use this vulnerability with
VIGILANCE-VUL-8953 (https://vigilance.fr/tree/1/8953)/VIGILANCE-VUL-8861
(https://vigilance.fr/tree/1/8861) in order to elevate his
privileges.
CHARACTERISTICS
– Identifiers: 527534, BID-36639, CVE-2009-2908, VIGILANCE-VUL-9075
– Url: http://vigilance.fr/vulnerability/Linux-kernel-privilege-elevation-via-eCryptfs-9075