[PATCH V2] efi/tpm: Fix the issue where the CC platforms event log header can't be correctly identified

[yangge1116@126.com]

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.

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@126.com>
Cc: stable@vger.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