在 2025/7/8 9:19, Ard Biesheuvel 写道:
On Mon, 7 Jul 2025 at 13:15, 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. 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-... Link: https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClient_PFP_r1p05_... 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
V3:
- fix build error
V2:
limit the fix for CC only suggested by Jarkko and Sathyanarayanan
drivers/char/tpm/eventlog/tpm2.c | 4 +++- drivers/firmware/efi/libstub/tpm.c | 13 +++++++++---- drivers/firmware/efi/tpm.c | 4 +++- include/linux/tpm_eventlog.h | 14 +++++++++++--- 4 files changed, 26 insertions(+), 9 deletions(-)
diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c index 37a0580..30ef47c 100644 --- a/drivers/char/tpm/eventlog/tpm2.c +++ b/drivers/char/tpm/eventlog/tpm2.c @@ -18,6 +18,7 @@ #include <linux/module.h> #include <linux/slab.h> #include <linux/tpm_eventlog.h> +#include <linux/cc_platform.h>
#include "../tpm.h" #include "common.h" @@ -36,7 +37,8 @@ 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));
This conflates TDX attestation with guest state encryption.
I think there could be meaningful ways for a confidential guest to use [emulated] TPM attestation rather than CC specific attestation, so I don't think it is a good idea to assume that the fact that we are running on a CoCo guest always implies that all the TCG data structures are of the CC variety.
Okay, thank you. I'll adjust the patch again.
}
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,
{ efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID; efi_status_t status;bool is_cc_event)
@@ -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..ca8535d 100644 --- a/drivers/firmware/efi/tpm.c +++ b/drivers/firmware/efi/tpm.c @@ -12,6 +12,7 @@ #include <linux/init.h> #include <linux/memblock.h> #include <linux/tpm_eventlog.h> +#include <linux/cc_platform.h>
int efi_tpm_final_log_size; EXPORT_SYMBOL(efi_tpm_final_log_size); @@ -23,7 +24,8 @@ 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,
{ struct tcg_efi_specid_event_head *efispecid; struct tcg_event_field *event_field;bool is_cc_event)
@@ -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