diff mbox series

[v2,2/3] tpm: acpi: Check eventlog signature before using it

Message ID 20210310221916.356716-3-stefanb@linux.ibm.com (mailing list archive)
State New
Headers show
Series Fix bugs related to TPM2 event log | expand

Commit Message

Stefan Berger March 10, 2021, 10:19 p.m. UTC
Check the eventlog signature before using it. This avoids using an
empty log, as may be the case when QEMU created the ACPI tables,
rather than probing the EFI log next. This resolves an issue where
the EFI log was empty since an empty ACPI log was used.

Fixes: 85467f63a05c ("tpm: Add support for event log pointer found in TPM2 ACPI table")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 drivers/char/tpm/eventlog/acpi.c | 33 +++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

Comments

Jarkko Sakkinen March 10, 2021, 11:13 p.m. UTC | #1
On Wed, Mar 10, 2021 at 05:19:15PM -0500, Stefan Berger wrote:
> Check the eventlog signature before using it. This avoids using an
> empty log, as may be the case when QEMU created the ACPI tables,
> rather than probing the EFI log next. This resolves an issue where
> the EFI log was empty since an empty ACPI log was used.
> 
> Fixes: 85467f63a05c ("tpm: Add support for event log pointer found in TPM2 ACPI table")
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  drivers/char/tpm/eventlog/acpi.c | 33 +++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/eventlog/acpi.c b/drivers/char/tpm/eventlog/acpi.c
> index 3633ed70f48f..1b18ce5ebab1 100644
> --- a/drivers/char/tpm/eventlog/acpi.c
> +++ b/drivers/char/tpm/eventlog/acpi.c
> @@ -41,6 +41,27 @@ struct acpi_tcpa {
>  	};
>  };
>  
> +/* Check that the given log is indeed a TPM2 log. */
> +static bool tpm_is_tpm2_log(void *bios_event_log, u64 len)
> +{
> +	struct tcg_efi_specid_event_head *efispecid;
> +	struct tcg_pcr_event *event_header;
> +	int n;
> +
> +	if (len < sizeof(*event_header))
> +		return false;
> +	len -= sizeof(*event_header);
> +	event_header = bios_event_log;
> +
> +	if (len < sizeof(*efispecid))
> +		return false;
> +	efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
> +
> +	n = memcmp(efispecid->signature, TCG_SPECID_SIG,
> +		   sizeof(TCG_SPECID_SIG));
> +	return n == 0;
> +}
> +
>  /* read binary bios log */
>  int tpm_read_log_acpi(struct tpm_chip *chip)
>  {
> @@ -52,6 +73,7 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
>  	struct acpi_table_tpm2 *tbl;
>  	struct acpi_tpm2_phy *tpm2_phy;
>  	int format;
> +	int ret;
>  
>  	log = &chip->log;
>  
> @@ -112,6 +134,7 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
>  
>  	log->bios_event_log_end = log->bios_event_log + len;
>  
> +	ret = -EIO;
>  	virt = acpi_os_map_iomem(start, len);
>  	if (!virt)
>  		goto err;
> @@ -119,11 +142,19 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
>  	memcpy_fromio(log->bios_event_log, virt, len);
>  
>  	acpi_os_unmap_iomem(virt, len);
> +
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2 &&
> +	    !tpm_is_tpm2_log(log->bios_event_log, len)) {
> +		/* try EFI log next */
> +		ret = -ENODEV;
> +		goto err;
> +	}
> +
>  	return format;
>  
>  err:
>  	kfree(log->bios_event_log);
>  	log->bios_event_log = NULL;
> -	return -EIO;
> +	return ret;
>  
>  }
> -- 
> 2.29.2
> 
> 

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

/Jarkko
diff mbox series

Patch

diff --git a/drivers/char/tpm/eventlog/acpi.c b/drivers/char/tpm/eventlog/acpi.c
index 3633ed70f48f..1b18ce5ebab1 100644
--- a/drivers/char/tpm/eventlog/acpi.c
+++ b/drivers/char/tpm/eventlog/acpi.c
@@ -41,6 +41,27 @@  struct acpi_tcpa {
 	};
 };
 
+/* Check that the given log is indeed a TPM2 log. */
+static bool tpm_is_tpm2_log(void *bios_event_log, u64 len)
+{
+	struct tcg_efi_specid_event_head *efispecid;
+	struct tcg_pcr_event *event_header;
+	int n;
+
+	if (len < sizeof(*event_header))
+		return false;
+	len -= sizeof(*event_header);
+	event_header = bios_event_log;
+
+	if (len < sizeof(*efispecid))
+		return false;
+	efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
+
+	n = memcmp(efispecid->signature, TCG_SPECID_SIG,
+		   sizeof(TCG_SPECID_SIG));
+	return n == 0;
+}
+
 /* read binary bios log */
 int tpm_read_log_acpi(struct tpm_chip *chip)
 {
@@ -52,6 +73,7 @@  int tpm_read_log_acpi(struct tpm_chip *chip)
 	struct acpi_table_tpm2 *tbl;
 	struct acpi_tpm2_phy *tpm2_phy;
 	int format;
+	int ret;
 
 	log = &chip->log;
 
@@ -112,6 +134,7 @@  int tpm_read_log_acpi(struct tpm_chip *chip)
 
 	log->bios_event_log_end = log->bios_event_log + len;
 
+	ret = -EIO;
 	virt = acpi_os_map_iomem(start, len);
 	if (!virt)
 		goto err;
@@ -119,11 +142,19 @@  int tpm_read_log_acpi(struct tpm_chip *chip)
 	memcpy_fromio(log->bios_event_log, virt, len);
 
 	acpi_os_unmap_iomem(virt, len);
+
+	if (chip->flags & TPM_CHIP_FLAG_TPM2 &&
+	    !tpm_is_tpm2_log(log->bios_event_log, len)) {
+		/* try EFI log next */
+		ret = -ENODEV;
+		goto err;
+	}
+
 	return format;
 
 err:
 	kfree(log->bios_event_log);
 	log->bios_event_log = NULL;
-	return -EIO;
+	return ret;
 
 }