On Mon, Mar 08, 2021 at 10:19:53PM -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@xxxxxxxxxxxxx>
> ---
> drivers/char/tpm/eventlog/acpi.c | 31 ++++++++++++++++++++++++++++++-
> 1 file changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/eventlog/acpi.c b/drivers/char/tpm/eventlog/acpi.c
> index 3633ed70f48f..b6bfd22e4a2f 100644
> --- a/drivers/char/tpm/eventlog/acpi.c
> +++ b/drivers/char/tpm/eventlog/acpi.c
> @@ -41,6 +41,25 @@ struct acpi_tcpa {
> };
> };
>
> +/* check that the given log is indeed a TPM2 log */
/* Check that the given log is indeed a TPM2 log. */
> +static int tpm_check_tpm2_log_header(void *bios_event_log, u64 len)
Just by this name does not give any clue what the function does.
"check" can refer to almost anything.
Perhaps just tpm_is_tpm2_log()?
> +{
> + struct tcg_efi_specid_event_head *efispecid;
> + struct tcg_pcr_event *event_header = bios_event_log;
Please, reorder these declarations (reverse christmas tree).
> +
> + if (len < sizeof(*event_header))
> + return 1;
> + len -= sizeof(*event_header);
> +
> + efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
> + if (len < sizeof(*efispecid) ||
> + memcmp(efispecid->signature, TCG_SPECID_SIG,
> + sizeof(TCG_SPECID_SIG)))
Please never put memcmp() inside a conditional statement.
> + return 1;
> +
> + return 0;
> +}
> +
> /* read binary bios log */
> int tpm_read_log_acpi(struct tpm_chip *chip)
> {
> @@ -52,6 +71,7 @@ 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 +132,7 @@ 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 +140,19 @@ 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_check_tpm2_log_header(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
>
>
/Jarkko
