Re: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound violation information

Thomas Gleixner
2014-10-31T09:09:13Z

On Fri, 31 Oct 2014, Ren Qiaowei wrote:
> On 10/31/2014 06:38 AM, Dave Hansen wrote:
> > > @@ -316,6 +317,11 @@ dotraplinkage void do_bounds(struct pt_regs *regs,
> > > long error_code)
> > > break;
> > >
> > > case 1: /* Bound violation. */
> > > + do_mpx_bounds(regs, &info, xsave_buf);
> > > + do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs,
> > > + error_code, &info);
> > > + break;
> > > +
> > > case 0: /* No exception caused by Intel MPX operations. */
> > > do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code,
> > > NULL);
> > > break;
> > >
> >
> > So, siginfo is stack-allocarted here. do_mpx_bounds() can error out if
> > it sees an invalid bndregno. We still send the signal with the &info
> > whether or not we filled the 'info' in do_mpx_bounds().
> >
> > Can't this leak some kernel stack out in the 'info'?
> >
>
> This should check the return value of do_mpx_bounds and should be fixed.

And how's that answering Dave's question about leaking stack information?

Thanks,

tglx