2014-10-03 01:10+0300, Nadav Amit:
> When read access is performed using a readable code segment, the "conforming"
> and "non-conforming" checks should not be done. As a result, read using
> non-conforming readable code segment fails.
>
> This is according to Intel SDM 5.6.1 ("Accessing Data in Code Segments").
(Checks are neccessarily true, except for non-conforming readable code,
which is to be treated like a data segment.)
> The fix is not to perform the "non-conforming" checks if the access is not a
> fetch.
(Because 'fetch' implies correct conditions and the rest is checked when
loading the segment,)
> Signed-off-by: Nadav Amit <na...@cs.technion.ac.il>
> ---
Reviewed-by: Radim Krčmář <rkrc...@redhat.com>
> arch/x86/kvm/emulate.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index a46207a..694dfa7 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -661,8 +661,8 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
> goto bad;
> }
> cpl = ctxt->ops->cpl(ctxt);
> - if (!(desc.type & 8)) {
> - /* data segment */
> + if (!fetch) {
> + /* data segment or readable code segment */
> if (cpl > desc.dpl)
> goto bad;
> } else if ((desc.type & 8) && !(desc.type & 4)) {
> --
> 1.9.1
>
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