CVE-2015-2925

Published: 6 April 2015

The prepend_path function in fs/dcache.c in the Linux kernel before 4.2.4 does not properly handle rename actions inside a bind mount, which allows local users to bypass an intended container protection mechanism by renaming a directory, related to a "double-chroot attack."

From the Ubuntu Security Team

It was discovered that in certain situations, a directory could be renamed outside of a bind mounted location. An attacker could use this to escape bind mount containment and gain access to sensitive information.

Notes

android kernels (flo, goldfish, grouper, maguro, mako and manta) are
not supported on the Ubuntu Touch 14.10 and earlier preview kernels
linux-lts-saucy no longer receives official support
linux-lts-quantal no longer receives official support

See gmane-151103 article for more backport discussion, specifically
that Eric B.'s backport eliminates the requirement for this patch:
70291ae namei: lift (open-coded) terminate_walk() in follow_dotdot_rcu() into callers

Status

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-2925
• http://permalink.gmane.org/gmane.linux.kernel.containers/29173
• http://permalink.gmane.org/gmane.linux.kernel.containers/29177
• http://article.gmane.org/gmane.linux.kernel.stable/151103
• https://ubuntu.com/security/notices/USN-2794-1
• https://ubuntu.com/security/notices/USN-2792-1
• https://ubuntu.com/security/notices/USN-2795-1
• https://ubuntu.com/security/notices/USN-2799-1
• https://ubuntu.com/security/notices/USN-2796-1
• https://ubuntu.com/security/notices/USN-2798-1
• https://ubuntu.com/security/notices/USN-2797-1
• NVD
• Launchpad
• Debian

Bugs

• https://launchpad.net/bugs/1441108