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Message-Id: <1751710616-24464-1-git-send-email-yangge1116@126.com>
Date: Sat, 5 Jul 2025 18:16:56 +0800
From: yangge1116@....com
To: ardb@...nel.org
Cc: jarkko@...nel.org,
sathyanarayanan.kuppuswamy@...ux.intel.com,
ilias.apalodimas@...aro.org,
jgg@...pe.ca,
linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org,
stable@...r.kernel.org,
liuzixing@...on.cn,
Ge Yang <yangge1116@....com>
Subject: [PATCH V2] efi/tpm: Fix the issue where the CC platforms event log header can't be correctly identified
From: Ge Yang <yangge1116@....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.
According to Table 6 in Section 10.2.1 of the TCG PC Client
Specification, the index field does not require the PCR index to be
fixed at zero. Therefore, skipping the check for a pcr_idx value of
0 for CC platforms is safe.
Link: https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#intel-trust-domain-extension
Link: https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClient_PFP_r1p05_v23_pub.pdf
Fixes: d228814b1913 ("efi/libstub: Add get_event_log() support for CC platforms")
Signed-off-by: Ge Yang <yangge1116@....com>
Cc: stable@...r.kernel.org
---
V2:
- limit the fix for CC only suggested by Jarkko and Sathyanarayanan
drivers/char/tpm/eventlog/tpm2.c | 3 ++-
drivers/firmware/efi/libstub/tpm.c | 13 +++++++++----
drivers/firmware/efi/tpm.c | 3 ++-
include/linux/tpm_eventlog.h | 14 +++++++++++---
4 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c
index 37a0580..87a8b7f 100644
--- a/drivers/char/tpm/eventlog/tpm2.c
+++ b/drivers/char/tpm/eventlog/tpm2.c
@@ -36,7 +36,8 @@
static size_t calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
struct tcg_pcr_event *event_header)
{
- return __calc_tpm2_event_size(event, event_header, false);
+ return __calc_tpm2_event_size(event, event_header, false,
+ cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT));
}
static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
index a5c6c4f..9728060 100644
--- a/drivers/firmware/efi/libstub/tpm.c
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -50,7 +50,8 @@ void efi_enable_reset_attack_mitigation(void)
static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_location,
efi_physical_addr_t log_last_entry,
efi_bool_t truncated,
- struct efi_tcg2_final_events_table *final_events_table)
+ struct efi_tcg2_final_events_table *final_events_table,
+ bool is_cc_event)
{
efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
efi_status_t status;
@@ -87,7 +88,8 @@ static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_loca
last_entry_size =
__calc_tpm2_event_size((void *)last_entry_addr,
(void *)(long)log_location,
- false);
+ false,
+ is_cc_event);
} else {
last_entry_size = sizeof(struct tcpa_event) +
((struct tcpa_event *) last_entry_addr)->event_size;
@@ -123,7 +125,8 @@ static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_loca
header = data + offset + final_events_size;
event_size = __calc_tpm2_event_size(header,
(void *)(long)log_location,
- false);
+ false,
+ is_cc_event);
/* If calc fails this is a malformed log */
if (!event_size)
break;
@@ -157,6 +160,7 @@ void efi_retrieve_eventlog(void)
efi_tcg2_protocol_t *tpm2 = NULL;
efi_bool_t truncated;
efi_status_t status;
+ bool is_cc_event = false;
status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2);
if (status == EFI_SUCCESS) {
@@ -186,11 +190,12 @@ void efi_retrieve_eventlog(void)
final_events_table =
get_efi_config_table(EFI_CC_FINAL_EVENTS_TABLE_GUID);
+ is_cc_event = true;
}
if (status != EFI_SUCCESS || !log_location)
return;
efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry,
- truncated, final_events_table);
+ truncated, final_events_table, is_cc_event);
}
diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
index cdd4310..a94816d 100644
--- a/drivers/firmware/efi/tpm.c
+++ b/drivers/firmware/efi/tpm.c
@@ -23,7 +23,8 @@ static int __init tpm2_calc_event_log_size(void *data, int count, void *size_inf
while (count > 0) {
header = data + size;
- event_size = __calc_tpm2_event_size(header, size_info, true);
+ event_size = __calc_tpm2_event_size(header, size_info, true,
+ cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT));
if (event_size == 0)
return -1;
size += event_size;
diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 891368e..b3380c9 100644
--- a/include/linux/tpm_eventlog.h
+++ b/include/linux/tpm_eventlog.h
@@ -143,6 +143,7 @@ struct tcg_algorithm_info {
* @event: Pointer to the event whose size should be calculated
* @event_header: Pointer to the initial event containing the digest lengths
* @do_mapping: Whether or not the event needs to be mapped
+ * @is_cc_event: Whether or not the event is from a CC platform
*
* The TPM2 event log format can contain multiple digests corresponding to
* separate PCR banks, and also contains a variable length of the data that
@@ -159,7 +160,8 @@ struct tcg_algorithm_info {
static __always_inline u32 __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
struct tcg_pcr_event *event_header,
- bool do_mapping)
+ bool do_mapping,
+ bool is_cc_event)
{
struct tcg_efi_specid_event_head *efispecid;
struct tcg_event_field *event_field;
@@ -201,8 +203,14 @@ static __always_inline u32 __calc_tpm2_event_size(struct tcg_pcr_event2_head *ev
count = event->count;
event_type = event->event_type;
- /* Verify that it's the log header */
- if (event_header->pcr_idx != 0 ||
+ /*
+ * Verify that it's the log header. According to the TCG PC Client
+ * Specification, when identifying a log header, the check for a
+ * pcr_idx value of 0 is not required. For CC platforms, skipping
+ * this check during log header is necessary; otherwise, the CC
+ * platform's log header may fail to be recognized.
+ */
+ if ((!is_cc_event && event_header->pcr_idx != 0) ||
event_header->event_type != NO_ACTION ||
memcmp(event_header->digest, zero_digest, sizeof(zero_digest))) {
size = 0;
--
2.7.4
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