[PATCH V5] efi/tpm: Fix the issue where the CC platforms event log header can't be correctly identified
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.
According to UEFI Specification 2.10, Section 38.4.1: For TDX, TPM PCR 0 maps to MRTD, so the log header uses TPM PCR 1 instead. To successfully parse the TDX event log header, the check for a pcr_idx value of 0 must be skipped. There's no danger of this causing problems because we check for the TCG_SPECID_SIG signature as the next thing.
Link: https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#intel-trust-... 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 --- 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;
On Sat, 2025-07-12 at 10:55 +0800, yangge1116@126.com wrote:
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.
According to UEFI Specification 2.10, Section 38.4.1: For TDX, TPM PCR 0 maps to MRTD, so the log header uses TPM PCR 1 instead.
This isn't a justification ... Intel just screwed up. Whatever the UEFI spec says about PCR mapping, the log spec the TCG produces requires the header event to have a pcrIndex of 0 and, since it isn't recorded in a PCR, it doesn't matter what the mapping is.
Just say 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.
Regards,
James
在 2025/7/12 11:03, James Bottomley 写道:
On Sat, 2025-07-12 at 10:55 +0800, yangge1116@126.com wrote:
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.
According to UEFI Specification 2.10, Section 38.4.1: For TDX, TPM PCR 0 maps to MRTD, so the log header uses TPM PCR 1 instead.
This isn't a justification ... Intel just screwed up. Whatever the UEFI spec says about PCR mapping, the log spec the TCG produces requires the header event to have a pcrIndex of 0 and, since it isn't recorded in a PCR, it doesn't matter what the mapping is.
Just say 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.
OK, thanks.
Regards,
James
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