Re: [v6 PATCH 04/21] x86/mpx, x86/insn: Relocate insn util functions to a new insn-kernel

[Ricardo Neri]

On Wed, 2017-04-12 at 12:03 +0200, Borislav Petkov wrote:
> > +              * If mod is 0 and register R/EBP (regno=5) is
> indicated in the
> > +              * base part of the SIB byte, the value of such
> register should
> > +              * not be used in the address computation. Also, a
> 32-bit
> > +              * displacement is expected in this case; the
> instruction
> > +              * decoder takes care of it. This is true for both R13
> and
> > +              * R/EBP as REX.B will not be decoded.
> > +              */
> > +             if (regno == 5 && X86_MODRM_MOD(insn->modrm.value) ==
> 0)
> > +                     return -EDOM;
> > +
> > +             if (X86_REX_B(insn->rex_prefix.value))
> > +                     regno += 8;
> > +             break;
> > +
> > +     default:
> > +             pr_err("invalid register type");
> > +             BUG();
> 
> WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code
> rather than BUG() or BUG_ON()
> #211: FILE: arch/x86/lib/insn-eval.c:90:
> +               BUG();
> 
> And checkpatch is kinda right. We need to warn here, not explode. Oh
> and
> that function returns negative values on error...
> 
> Please change that with a patch ontop of the move.

Sure, I will change it.