linux-kernel - [PATCH] efi/tpm: Differentiate missing and invalid final event log table.

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Message-Id: <20210708094654.4157-1-msuchanek@suse.de>
Date:   Thu,  8 Jul 2021 11:46:54 +0200
From:   Michal Suchanek <msuchanek@...e.de>
To:     linux-integrity@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>
Cc:     Michal Suchanek <msuchanek@...e.de>,
        Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Loïc Yhuel <loic.yhuel@...il.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] efi/tpm: Differentiate missing and invalid final event log table.

Missing TPM final event log table is not a firmware bug.

Clearly if providing event log in the old format makes the final event
log invalid it should not be provided at least in that case.

Fixes: b4f1874c6216 ("tpm: check event log version before reading final events")
Signed-off-by: Michal Suchanek <msuchanek@...e.de>
---
 drivers/firmware/efi/tpm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
index c1955d320fec..8f665678e9e3 100644
--- a/drivers/firmware/efi/tpm.c
+++ b/drivers/firmware/efi/tpm.c
@@ -62,9 +62,11 @@ int __init efi_tpm_eventlog_init(void)
 	tbl_size = sizeof(*log_tbl) + log_tbl->size;
 	memblock_reserve(efi.tpm_log, tbl_size);
 
-	if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR ||
-	    log_tbl->version != EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) {
-		pr_warn(FW_BUG "TPM Final Events table missing or invalid\n");
+	if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) {
+		pr_info("TPM Final Events table not present\n");
+		goto out;
+	} else if (log_tbl->version != EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) {
+		pr_warn(FW_BUG "TPM Final Events table invalid\n");
 		goto out;
 	}
 
-- 
2.26.2