CVE-2014-5045

The mountpoint_last function in fs/namei.c in the Linux kernel before 3.15.8 does not properly maintain a certain reference count during attempts to use the umount system call in conjunction with a symlink, which allows local users to cause a denial of service (memory consumption or use-after-free) or possibly have unspecified other impact via the umount program.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=295dc39d941dc2ae53d5c170365af4c9d5c16212
• http://rhn.redhat.com/errata/RHSA-2015-0062.html
• http://secunia.com/advisories/60353
• http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.15.8
• http://www.openwall.com/lists/oss-security/2014/07/24/2
• http://www.securityfocus.com/bid/68862
• https://bugzilla.redhat.com/show_bug.cgi?id=1122472
• https://github.com/torvalds/linux/commit/295dc39d941dc2ae53d5c170365af4c9d5c16212