From: Ge Yang yangge1116@126.com

Since commit d228814b1913 ("efi/libstub: Add get_event_log() support for CC platforms") reuses TPM2 support code for the CC platforms, when launching a TDX virtual machine with coco measurement enabled, the following error log is generated:

[Firmware Bug]: Failed to parse event in TPM Final Events Log

Call Trace: efi_config_parse_tables() efi_tpm_eventlog_init() tpm2_calc_event_log_size() __calc_tpm2_event_size()

The pcr_idx value in the Intel TDX log header is 1, causing the function __calc_tpm2_event_size() to fail to recognize the log header, ultimately leading to the "Failed to parse event in TPM Final Events Log" error.

Intel misread the spec and wrongly sets pcrIndex to 1 in the header and since they did this, we fear others might, so we're relaxing the header check. There's no danger of this causing problems because we check for the TCG_SPECID_SIG signature as the next thing.

Fixes: d228814b1913 ("efi/libstub: Add get_event_log() support for CC platforms") Signed-off-by: Ge Yang yangge1116@126.com Cc: stable@vger.kernel.org ---

V6: - improve commit message suggested by James

V5: - remove the pcr_index check without adding any replacement checks suggested by James and Sathyanarayanan

V4: - remove cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT) suggested by Ard

V3: - fix build error

V2: - limit the fix for CC only suggested by Jarkko and Sathyanarayanan

include/linux/tpm_eventlog.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h index 891368e..05c0ae5 100644 --- a/include/linux/tpm_eventlog.h +++ b/include/linux/tpm_eventlog.h @@ -202,8 +202,7 @@ static __always_inline u32 __calc_tpm2_event_size(struct tcg_pcr_event2_head *ev event_type = event->event_type;

/* Verify that it's the log header */ - if (event_header->pcr_idx != 0 || - event_header->event_type != NO_ACTION || + if (event_header->event_type != NO_ACTION || memcmp(event_header->digest, zero_digest, sizeof(zero_digest))) { size = 0; goto out;