The nfs_can_extend_write function in fs/nfs/write.c in the Linux kernel before 3.13.3 relies on a write delegation to extend a write operation without a certain up-to-date verification, which allows local users to obtain sensitive information from kernel memory in opportunistic circumstances by writing to a file in an NFS filesystem and then reading the same file.

References

• https://nvd.nist.gov/vuln/detail/CVE-2014-2038
• torvalds/linux@263b450
• https://bugzilla.redhat.com/show_bug.cgi?id=1066939
• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=263b4509ec4d47e0da3e753f85a39ea12d1eff24
• http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.13.3
• http://www.openwall.com/lists/oss-security/2014/02/20/16
• http://www.ubuntu.com/usn/USN-2137-1
• http://www.ubuntu.com/usn/USN-2140-1
• http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=263b4509ec4d47e0da3e753f85a39ea12d1eff24