CVE-2015-8839: Race Condition
A flaw was found in the Linux kernel when attempting to "punch a hole" in files existing on an ext4 filesystem. When punching holes into a file races with the page fault of the same area, it is possible that freed blocks remain referenced from page cache pages mapped to process' address space.
Thus modification of these blocks can corrupt data someone else is now storing in those blocks when at some point those pages are written to disk.
Upstream fixes:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ea3d7209ca01da209cda6f0dea8be9cc4b7a933b http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17048e8a083fec7ad841d88ef0812707fbc7e39f http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=32ebffd3bbb4162da5ff88f9a35dd32d0a28ea70 http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=011278485ecc3cd2a3954b5d4c73101d919bf1fa
References:
http://seclists.org/oss-sec/2016/q2/1
Other sources
Multiple race conditions in the ext4 filesystem implementation in the Linux kernel before 4.5 allow local users to cause a denial of service (disk corruption) by writing to a page that is associated with a different user's file after unsynchronized hole punching and page-fault handling.
— Launchpad
Affected Software
Remediation
Event History
Frequently Asked Questions
What is CVE-2015-8839?
CVE-2015-8839 is a vulnerability in the ext4 filesystem implementation in the Linux kernel before version 4.5 that allows local users to cause a denial of service (disk corruption).
How severe is CVE-2015-8839?
CVE-2015-8839 has a severity level of medium.
Which software is affected by CVE-2015-8839?
The affected software includes Linux kernel versions before 4.5.
How can I fix CVE-2015-8839?
To fix CVE-2015-8839, you should update your Linux kernel to version 4.5 or higher.
Where can I find more information about CVE-2015-8839?
You can find more information about CVE-2015-8839 on the following links: - [Link 1](http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ea3d7209ca01da209cda6f0dea8be9cc4b7a933b) - [Link 2](http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17048e8a083fec7ad841d88ef0812707fbc7e39f) - [Link 3](http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=32ebffd3bbb4162da5ff88f9a35dd32d0a28ea70)