• Dave Hansen's avatar
    x86/mpx: Fix instruction decoder condition · 8e8efe03
    Dave Hansen authored
    MPX decodes instructions in order to tell which bounds register
    was violated.  Part of this decoding involves looking at the "REX
    prefix" which is a special instrucion prefix used to retrofit
    support for new registers in to old instructions.
    
    The X86_REX_*() macros are defined to return actual bit values:
    
    	#define X86_REX_R(rex) ((rex) & 4)
    
    *not* boolean values.  However, the MPX code was checking for
    them like they were booleans.  This might have led to us
    mis-decoding the "REX prefix" and giving false information out to
    userspace about bounds violations.  X86_REX_B() actually is bit 1,
    so this is really only broken for the X86_REX_X() case.
    
    Fix the conditionals up to tolerate the non-boolean values.
    
    Fixes: fcc7ffd6 "x86, mpx: Decode MPX instruction to get bound violation information"
    Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
    Cc: x86@kernel.org
    Cc: Dave Hansen <dave@sr71.net>
    Cc: stable@vger.kernel.org
    Link: http://lkml.kernel.org/r/20151201003113.D800C1E0@viggo.jf.intel.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    8e8efe03
mpx.c 28 KB