PRE-CERT Security Advisory

• Advisory: PRE-SA-2012-03
• Released on: 10 May 2012
• Affected product: Linux Kernel 3.3.x <= 3.3.4
  2.6.x <= 2.6.35.13
• Impact: code execution / privilege escalation
• Origin: HFS plus file system
• Credit: Timo Warns (PRESENSE Technologies GmbH)
• CVE Identifier: CVE-2012-2319

Summary

The Linux kernel contains a vulnerability in the driver for HFS plus
file systems that may be exploited for code execution or privilege
escalation.

A specially-crafted HFS plus filesystem can cause a buffer overflow via
the memcpy() call of hfs_bnode_read() (in fs/hfsplus/bnode.c). The
functions

hfsplus_rename_cat() (in fs/hfsplus/catalog.c) and
hfsplus_readdir() (in fs/hfsplus/dir.c)

call hfs_bnode_read() with values that result in a memcpy() call with
a fixed-length destination buffer and both, a source buffer and length,
that are read from the filesystem without sufficient validation.

The buffer overflows were previously fixed in the HFS filesystem driver
and have been assigned CVE-2009-4020
(commit ec81aecb29668ad71f699f4e7b96ec46691895b6 [1]).
Commit 6f24f892871acc47b40dd594c63606a17c714f77 ("hfsplus: fix
a potential buffer overflow") [2] also fixes the issue in the HFS plus
filesystem driver.

Workaround

Compile and use a kernel that does not support the HFS plus file system.
The corresponding configuration key is CONFIG_HFSPLUS_FS.

Solution

A patch is available at
http://git.kernel.org/linus/6f24f892871acc47b40dd594c63606a17c714f77

The issue has been fixed in Linux 3.3.5.

References

[1] http://git.kernel.org/linus/ec81aecb29668ad71f699f4e7b96ec46691895b6
[2] http://git.kernel.org/linus/6f24f892871acc47b40dd594c63606a17c714f77

When further information becomes available, this advisory will be
updated. The most recent version of this advisory is available at:

http://www.pre-cert.de/advisories/PRE-SA-2012-03.txt

Contact

PRE-CERT can be reached under [email protected]. For PGP key
information, refer to http://www.pre-cert.de/.