Comment 5 for bug 1328965

Here's the fix as committed to the 3.14.6 kernel:

( Taken from https://www.kernel.org/pub/linux/kernel/v3.0/ChangeLog-3.14.6 )

commit 461a8fe47232a42c5ba9e2ac57eed37df331a2e3
Author: Linus Torvalds <email address hidden>
Date: Wed May 14 16:33:54 2014 -0700

    x86-64, modify_ldt: Make support for 16-bit segments a runtime option

    commit fa81511bb0bbb2b1aace3695ce869da9762624ff upstream.

    Checkin:

    b3b42ac2cbae x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels

    disabled 16-bit segments on 64-bit kernels due to an information
    leak. However, it does seem that people are genuinely using Wine to
    run old 16-bit Windows programs on Linux.

    A proper fix for this ("espfix64") is coming in the upcoming merge
    window, but as a temporary fix, create a sysctl to allow the
    administrator to re-enable support for 16-bit segments.

    It adds a "/proc/sys/abi/ldt16" sysctl that defaults to zero (off). If
    you hit this issue and care about your old Windows program more than
    you care about a kernel stack address information leak, you can do

       echo 1 > /proc/sys/abi/ldt16

    as root (add it to your startup scripts), and you should be ok.

    The sysctl table is only added if you have COMPAT support enabled on
    x86-64, but I assume anybody who runs old windows binaries very much
    does that ;)

    Signed-off-by: H. Peter Anvin <email address hidden>
    Link: http://lkml.kernel.org/r/CA%<email address hidden>
    Signed-off-by: Greg Kroah-Hartman <email address hidden>