On Wed, 5 Jun 2019 at 20:05, Matthew Garrett <[email protected]> wrote:
>
> After the first call to GetEventLog() on UEFI systems using the TCG2
> crypto agile log format, any further log events (other than those
> triggered by ExitBootServices()) will be logged in both the main log and
> also in the Final Events Log. While the kernel only calls GetEventLog()
> immediately before ExitBootServices(), we can't control whether earlier
> parts of the boot process have done so. This will result in log entries
> that exist in both logs, and so the current approach of simply appending
> the Final Event Log to the main log will result in events being
> duplicated.
>
> We can avoid this problem by looking at the size of the Final Event Log
> just before we call ExitBootServices() and exporting this to the main
> kernel. The kernel can then skip over all events that occured before
> ExitBootServices() and only append events that were not also logged to
> the main log.
>
> Signed-off-by: Matthew Garrett <[email protected]>
> Reported-by: Joe Richey <[email protected]>
> Suggested-by: Joe Richey <[email protected]>
> ---
>
> Unmodified other than changing the name of final_events_early_size to
> final_events_preboot_size.
>
> drivers/char/tpm/eventlog/efi.c | 11 ++++++-
> .../firmware/efi/libstub/efi-stub-helper.c | 15 ++++++++++
> drivers/firmware/efi/libstub/efistub.h | 2 ++
> drivers/firmware/efi/libstub/fdt.c | 27 ++++++-----------
> drivers/firmware/efi/libstub/tpm.c | 30 +++++++++++++++++++
> drivers/firmware/efi/tpm.c | 2 +-
> include/linux/efi.h | 1 +
> 7 files changed, 68 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/char/tpm/eventlog/efi.c b/drivers/char/tpm/eventlog/efi.c
> index 9179cf6bdee9..be6540f2cb3d 100644
> --- a/drivers/char/tpm/eventlog/efi.c
> +++ b/drivers/char/tpm/eventlog/efi.c
> @@ -80,6 +80,8 @@ int tpm_read_log_efi(struct tpm_chip *chip)
> goto out;
> }
>
> + efi_tpm_final_log_size -= log_tbl->final_events_preboot_size;
> +
> tmp = krealloc(log->bios_event_log,
> log_size + efi_tpm_final_log_size,
> GFP_KERNEL);
> @@ -90,8 +92,15 @@ int tpm_read_log_efi(struct tpm_chip *chip)
> }
>
> log->bios_event_log = tmp;
> +
> + /*
> + * Copy any of the final events log that didn't also end up in the
> + * main log. Events can be logged in both if events are generated
> + * between GetEventLog() and ExitBootServices().
> + */
> memcpy((void *)log->bios_event_log + log_size,
> - final_tbl->events, efi_tpm_final_log_size);
> + final_tbl->events + log_tbl->final_events_preboot_size,
> + efi_tpm_final_log_size);
> log->bios_event_log_end = log->bios_event_log +
> log_size + efi_tpm_final_log_size;
>
> diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c
> b/drivers/firmware/efi/libstub/efi-stub-helper.c
> index e4610e72b78f..1db780c0f07b 100644
> --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
> +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
> @@ -926,3 +926,18 @@ efi_status_t efi_exit_boot_services(efi_system_table_t
> *sys_table_arg,
> fail:
> return status;
> }
> +
> +void *get_efi_config_table(efi_system_table_t *sys_table, efi_guid_t guid)
> +{
> + efi_config_table_t *tables = (efi_config_table_t *)sys_table->tables;
> + int i;
> +
> + for (i = 0; i < sys_table->nr_tables; i++) {
> + if (efi_guidcmp(tables[i].guid, guid) != 0)
> + continue;
> +
> + return (void *)tables[i].table;
> + }
> +
> + return NULL;
> +}
Please create a separate patch that factors out this code from get_fdt().
> diff --git a/drivers/firmware/efi/libstub/efistub.h
> b/drivers/firmware/efi/libstub/efistub.h
> index 1b1dfcaa6fb9..7f1556fd867d 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -65,6 +65,8 @@ efi_status_t check_platform_features(efi_system_table_t
> *sys_table_arg);
>
> efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg);
>
> +void *get_efi_config_table(efi_system_table_t *sys_table, efi_guid_t guid);
> +
> /* Helper macros for the usual case of using simple C variables: */
> #ifndef fdt_setprop_inplace_var
> #define fdt_setprop_inplace_var(fdt, node_offset, name, var) \
> diff --git a/drivers/firmware/efi/libstub/fdt.c
> b/drivers/firmware/efi/libstub/fdt.c
> index 5440ba17a1c5..0bf0190917e0 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -363,26 +363,17 @@ efi_status_t
> allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
>
> void *get_fdt(efi_system_table_t *sys_table, unsigned long *fdt_size)
> {
> - efi_guid_t fdt_guid = DEVICE_TREE_GUID;
> - efi_config_table_t *tables;
> - int i;
> + void *fdt;
>
> - tables = (efi_config_table_t *)sys_table->tables;
> + fdt = get_efi_config_table(sys_table, DEVICE_TREE_GUID);
>
> - for (i = 0; i < sys_table->nr_tables; i++) {
> - void *fdt;
> + if (!fdt)
> + return NULL;
>
> - if (efi_guidcmp(tables[i].guid, fdt_guid) != 0)
> - continue;
> -
> - fdt = (void *)tables[i].table;
> - if (fdt_check_header(fdt) != 0) {
> - pr_efi_err(sys_table, "Invalid header detected on
> UEFI supplied FDT, ignoring ...\n");
> - return NULL;
> - }
> - *fdt_size = fdt_totalsize(fdt);
> - return fdt;
> + if (fdt_check_header(fdt) != 0) {
> + pr_efi_err(sys_table, "Invalid header detected on UEFI
> supplied FDT, ignoring ...\n");
> + return NULL;
> }
> -
> - return NULL;
> + *fdt_size = fdt_totalsize(fdt);
> + return fdt;
> }
> diff --git a/drivers/firmware/efi/libstub/tpm.c
> b/drivers/firmware/efi/libstub/tpm.c
> index 6b3b507a54eb..6c900ba38ab1 100644
> --- a/drivers/firmware/efi/libstub/tpm.c
> +++ b/drivers/firmware/efi/libstub/tpm.c
> @@ -64,11 +64,13 @@ void efi_retrieve_tpm2_eventlog(efi_system_table_t
> *sys_table_arg)
> efi_status_t status;
> efi_physical_addr_t log_location = 0, log_last_entry = 0;
> struct linux_efi_tpm_eventlog *log_tbl = NULL;
> + struct efi_tcg2_final_events_table *final_events_table;
> unsigned long first_entry_addr, last_entry_addr;
> size_t log_size, last_entry_size;
> efi_bool_t truncated;
> int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
> void *tcg2_protocol = NULL;
> + int final_events_size = 0;
>
> status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
> &tcg2_protocol);
> @@ -134,8 +136,36 @@ void efi_retrieve_tpm2_eventlog(efi_system_table_t
> *sys_table_arg)
> return;
> }
>
> + /*
> + * Figure out whether any events have already been logged to the
> + * final events structure, and if so how much space they take up
> + */
> + final_events_table = get_efi_config_table(sys_table_arg,
> + LINUX_EFI_TPM_FINAL_LOG_GUID);
> + if (final_events_table && final_events_table->nr_events) {
> + struct tcg_pcr_event2_head *header;
> + int offset;
> + void *data;
> + int event_size;
> + int i = final_events_table->nr_events;
> +
> + data = (void *)final_events_table;
> + offset = sizeof(final_events_table->version) +
> + sizeof(final_events_table->nr_events);
> +
> + while (i) {
Please use i > 0 here to avoid surprises (nr_events is an u64)
> + header = data + offset + final_events_size;
> + event_size = __calc_tpm2_event_size(header,
> + (void *)(long)log_location,
> + false);
> + final_events_size += event_size;
> + i--;
> + }
> + }
> +
> memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
> log_tbl->size = log_size;
> + log_tbl->final_events_preboot_size = final_events_size;
> log_tbl->version = version;
> memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
>
> diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
> index 2c912ea08166..0bdceb5913aa 100644
> --- a/drivers/firmware/efi/tpm.c
> +++ b/drivers/firmware/efi/tpm.c
> @@ -76,7 +76,7 @@ int __init efi_tpm_eventlog_init(void)
> goto out;
> }
>
> - tbl_size = tpm2_calc_event_log_size(efi.tpm_final_log
> + tbl_size = tpm2_calc_event_log_size((void *)efi.tpm_final_log
> + sizeof(final_tbl->version)
> + sizeof(final_tbl->nr_events),
> final_tbl->nr_events,
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index e33c70a52a9d..2a26004a9bdb 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1703,6 +1703,7 @@ struct linux_efi_random_seed {
>
> struct linux_efi_tpm_eventlog {
> u32 size;
> + u32 final_events_preboot_size;
> u8 version;
> u8 log[];
> };
> --
> 2.22.0.rc1.311.g5d7573a151-goog
>
