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tpm: acpi: Check eventlog signature before using it

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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.

Cc: stable@vger.kernel.org
Fixes: 85467f63a0 ("tpm: Add support for event log pointer found in TPM2 ACPI table")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Stefan Berger 2021-03-10 17:19:15 -05:00 committed by Jarkko Sakkinen
parent 48cff270b0
commit 3dcd15665a
1 changed files with 32 additions and 1 deletions
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33
drivers/char/tpm/eventlog/acpi.c
View file

@ -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;
}