[PATCH v2] efi_loader: tcg2: Return success even when TPM device is not found

[Heinrich Schuchardt]

On 11/29/21 15:55, Ilias Apalodimas wrote:
> On Mon, 29 Nov 2021 at 16:26, Michal Simek <michal.simek at xilinx.com> wrote:
>>
>> For systems which have TPM support enabled but actual device is missing
>> there is no reason to show a message that measurement failed in
>> efi_load_pe(). To ensure that the patch is returning EFI_SUCCESS even for
>> cases where TPM device is not found.
>> The reason is that other parts of the code return also EFI_NOT_FOUND in
>> tcg2_measure_pe_image() (e.g efi_search_protocol) that's why this error
>> code can't be checked but still it needs to be reported.
>>
>> The same logic is also used in efi_tcg2_get_eventlog() added by
>> commit c8d0fd582576 ("efi_loader: Introduce eventlog support for
>> TCG2_PROTOCOL").
>>
>> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
>> ---
>>
>> Changes in v2:
>> - Change subject and description
>> - Change logic in different location
>> - Origin thread was https://lore.kernel.org/r/657a869c04e9b09e3bd2e6fd74ff94320b7fbe9b.1638191161.git.michal.simek@xilinx.com
>>
>>   lib/efi_loader/efi_tcg2.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
>> index 8c1f22e3377b..db785f4d8c27 100644
>> --- a/lib/efi_loader/efi_tcg2.c
>> +++ b/lib/efi_loader/efi_tcg2.c
>> @@ -888,7 +888,8 @@ efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
>>
>>          ret = platform_get_tpm2_device(&dev);
>>          if (ret != EFI_SUCCESS)
>> -               return ret;
>> +               /* don't fail when TPM is not found */
>> +               return EFI_SUCCESS;
>>
>>          switch (handle->image_type) {
>>          case IMAGE_SUBSYSTEM_EFI_APPLICATION:
>> --
>> 2.33.1
>>
>
> Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
>

This patch means:

You can run some command that initializes the TCG2 protocol (e.g.
debug_hd), then unbind the TPM, run a first EFI binary which diverts EFI
API addresses, bind the TPM again and run the normal binary and nobody
will see the first binary in boot measurement.

Best regards

Heinrich