The Linux kernel before 3.11 on ARM platforms, as used in Android before 2016-08-05 on Nexus 5 and 7 (2013) devices, does not properly consider user-space access to the TPIDRURW register, which allows local users to gain privileges via a crafted application, aka Android internal bug 28749743 and Qualcomm internal bug CR561044.
https://source.codeaurora.org/quic/la/kernel/msm/commit/?id=4f57652fcd2dce7741f1ac6dc0417e2f265cd1de
https://github.com/torvalds/linux/commit/a4780adeefd042482f624f5e0d577bf9cdcbb760
http://www.securityfocus.com/bid/92219