Re: [Xen-devel] [PATCH 3/4] x86emul: drop pointless and add useful default cases

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 20/06/16 12:58, Jan Beulich wrote:
> @@ -3845,10 +3834,11 @@ x86_emulate(
>              goto push;
>          case 7:
>              generate_exception_if(1, EXC_UD, -1);
> -        default:
> -            goto cannot_emulate;
>          }
>          break;
> +
> +    default:
> +        BUG();

These introduce DoS vulnerabilities if there is indeed a path to default.

Could I recommend instead a one-time printk() dumping the instruction
stream which lead to here, an ASSERT_UNREACHABLE(), and a goto
cannot_emulate?

That way, a production build won't crash.

~Andrew

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