Re: [PATCH 6/6] libstub,tpm: do not ignore failure case when reading final event log

Ard Biesheuvel
2024-09-13T15:25:41Z

On Fri, 6 Sept 2024 at 22:28, Gregory Price <gourry@gourry.net> wrote:
>
> Current code fails to check for an error case when reading events from
> final event log to calculate offsets. Check the error case, report the
> error, and break early because all subsequent calls will also fail.
>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> ---
> drivers/firmware/efi/libstub/tpm.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
> index 4f9f0e049a7a..c71b0d3e66d2 100644
> --- a/drivers/firmware/efi/libstub/tpm.c
> +++ b/drivers/firmware/efi/libstub/tpm.c
> @@ -124,6 +124,10 @@ static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_loca
> event_size = __calc_tpm2_event_size(header,
> (void *)(long)log_location,
> false);
> + if (!event_size) {
> + efi_err("Invalid TPM Final Event Log Entry\n");
> + break;
> + }

I don't object to this in principle, the only problem is that these
log prints are not recorded anywhere: they are printed to the EFI boot
console by the EFI stub, which may not even be visible, and is
definitely not captured by the kernel logging routines.