Re: [PATCH] x86/loader: only patch linux kernels

[Michael S. Tsirkin]

On Wed, Apr 10, 2024 at 09:21:26AM +0200, Gerd Hoffmann wrote:
> If the binary loaded via -kernel is *not* a linux kernel (in which
> case protocol == 0), do not patch the linux kernel header fields.
> 
> It's (a) pointless and (b) might break binaries by random patching
> and (c) changes the binary hash which in turn breaks secure boot
> verification.
> 
> Background: OVMF happily loads and runs not only linux kernels but
> any efi binary via direct kernel boot.
> 
> Note: Breaking the secure boot verification is a problem for linux
> kernels too, but fixed that is left for another day ...

Um we kind of care about Linux ;)

What's the plan?  I suspect we should just add a command line flag
to skip patching? And once we do that, it seems safer to just
always rely on the flag?

> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/i386/x86.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index ffbda48917fd..765899eebe43 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -1108,7 +1108,7 @@ void x86_load_linux(X86MachineState *x86ms,
>       * kernel on the other side of the fw_cfg interface matches the hash of 
> the
>       * file the user passed in.
>       */
> -    if (!sev_enabled()) {
> +    if (!sev_enabled() && protocol > 0) {
>          memcpy(setup, header, MIN(sizeof(header), setup_size));
>      }
>  
> -- 
> 2.44.0