Re: [Xen-ia64-devel] VTi: break handling

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Tue, Apr 11, 2006 at 01:19:49PM +0100, Tristan Gingold wrote:
> Le Mardi 11 Avril 2006 13:59, Xu, Anthony a écrit :
> > >> It was used for debug.
> > >> Break 0, its opcode is 0,
> > >> Usually break 0 is not used by linux kernel and application.
> > >> When break 0 is executed, it usually means some thing wrong.
> > >
> > >Sure, but if an application does break 0, it locks up Xen!
> > >Maybe we should add a check.
> >
> > Normal application will not use break 0, right?
> Right and normal application does not crash too :-)
> Seriously, this is a security bug to me.  A user must not be able to locks up 
> an hypervisor!

Such a bug check can be done at vmx_ia64_handle_break().
ENTRY(vmx_break_fault)
    ...
    cmp.eq p6,p7=r30,r0          <<<<<<<<<<<<< remove
    (p6) br.sptk vmx_fault_11    <<<<<<<<<<<<< remove
    ;;                           <<<<<<<<<<<<<< remove

vmx_ia64_handle_break() 
    ....
    } else {
        if (iim == 0)  <<<<<<<<<<<<<<<<<<<<<<<<<< add precise check
            die_if_kernel("bug check", regs, iim);
        vmx_reflect_interruption(ifa,isr,iim,11,regs);
    }
    return IA64_NO_FAULT;


-- 
yamahata

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