Re: [PATCH v3 23/75] x86/boot/compressed/64: Setup GHCB Based VC Exception handler

Joerg Roedel
2020-06-03T10:08:57Z

On Mon, May 11, 2020 at 10:07:09PM +0200, Borislav Petkov wrote:
> On Tue, Apr 28, 2020 at 05:16:33PM +0200, Joerg Roedel wrote:
> > @@ -63,3 +175,45 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
> > while (true)
> > asm volatile("hlt\n");
> > }
> > +
> > +static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
> > + void *src, char *buf,
> > + unsigned int data_size,
> > + unsigned int count,
> > + bool backwards)
> > +{
> > + int i, b = backwards ? -1 : 1;
> > + enum es_result ret = ES_OK;
> > +
> > + for (i = 0; i < count; i++) {
> > + void *s = src + (i * data_size * b);
> > + char *d = buf + (i * data_size);
>
> >From a previous review:
>
> Where are we checking whether that count is not exceeding @buf or
> similar discrepancies?

These two functions are only called from vc_handle_ioio() and buf always
points to ghcb->shared_buffer.

In general, the caller has to make sure that sizeof(*buf) is at least
data_size*count, and handle_ioio() calculates count based on the size of
*buf.

Joerg