• Linus Torvalds's avatar
    x86-64, modify_ldt: Make support for 16-bit segments a runtime option · fa81511b
    Linus Torvalds authored
    Checkin:
    
    b3b42ac2 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: default avatarH. Peter Anvin <hpa@linux.intel.com>
    Link: http://lkml.kernel.org/r/CA%2B55aFw9BPoD10U1LfHbOMpHWZkvJTkMcfCs9s3urPr1YyWBxw@mail.gmail.com
    Cc: <stable@vger.kernel.org>
    fa81511b
vdso32-setup.c 6.39 KB