The xfs_fs_geometry function in fs/xfs/xfs_fsops.c in the Linux kernel
before 2.6.38-rc6-git3 does not initialize a certain structure member,
which allows local users to obtain potentially sensitive information from
kernel stack memory via an FSGEOMETRY_V1 ioctl call.

Dan Rosenberg discovered that XFS did not correctly initialize memory. A
local attacker could make crafted ioctl calls to leak portions of kernel
stack memory, leading to a loss of privacy.