The vsock_stream_sendmsg function in net/vmw_vsock/af_vsock.c in the Linux kernel before 3.9-rc7 does not initialize a certain length variable, which allows local users to obtain sensitive information from kernel stack memory via a crafted recvmsg or recvfrom system call.
https://lkml.org/lkml/2013/4/14/107
https://github.com/torvalds/linux/commit/d5e0d0f607a7a029c6563a0470d88255c89a8d11