tpm: Disable RNG for all AMD fTPMs

commit 554b841d470338a3b1d6335b14ee1cd0c8f5d754 upstream.

The TPM RNG functionality is not necessary for entropy when the CPU
already supports the RDRAND instruction. The TPM RNG functionality
was previously disabled on a subset of AMD fTPM series, but reports
continue to show problems on some systems causing stutter root caused
to TPM RNG functionality.

Expand disabling TPM RNG use for all AMD fTPMs whether they have versions
that claim to have fixed or not. To accomplish this, move the detection
into part of the TPM CRB registration and add a flag indicating that
the TPM should opt-out of registration to hwrng.

Cc: stable@vger.kernel.org # 6.1.y+
Fixes: b006c439d58d ("hwrng: core - start hwrng kthread also for untrusted sources")
Fixes: f1324bbc4011 ("tpm: disable hwrng for fTPM on some AMD designs")
Reported-by: daniil.stas@posteo.net
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217719
Reported-by: bitlord0xff@gmail.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217212
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index d7ef4d0a7409f3187e80f215656bc90952596710..64d3f8887169ab36bf9d79f1d2bc00c3c8bba12b 100644 (file)
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -507,70 +507,6 @@ static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
        return 0;
 }
 
-/*
- * Some AMD fTPM versions may cause stutter
- * https://www.amd.com/en/support/kb/faq/pa-410
- *
- * Fixes are available in two series of fTPM firmware:
- * 6.x.y.z series: 6.0.18.6 +
- * 3.x.y.z series: 3.57.y.5 +
- */
-#ifdef CONFIG_X86
-static bool tpm_amd_is_rng_defective(struct tpm_chip *chip)
-{
-       u32 val1, val2;
-       u64 version;
-       int ret;
-
-       if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
-               return false;
-
-       ret = tpm_request_locality(chip);
-       if (ret)
-               return false;
-
-       ret = tpm2_get_tpm_pt(chip, TPM2_PT_MANUFACTURER, &val1, NULL);
-       if (ret)
-               goto release;
-       if (val1 != 0x414D4400U /* AMD */) {
-               ret = -ENODEV;
-               goto release;
-       }
-       ret = tpm2_get_tpm_pt(chip, TPM2_PT_FIRMWARE_VERSION_1, &val1, NULL);
-       if (ret)
-               goto release;
-       ret = tpm2_get_tpm_pt(chip, TPM2_PT_FIRMWARE_VERSION_2, &val2, NULL);
-
-release:
-       tpm_relinquish_locality(chip);
-
-       if (ret)
-               return false;
-
-       version = ((u64)val1 << 32) | val2;
-       if ((version >> 48) == 6) {
-               if (version >= 0x0006000000180006ULL)
-                       return false;
-       } else if ((version >> 48) == 3) {
-               if (version >= 0x0003005700000005ULL)
-                       return false;
-       } else {
-               return false;
-       }
-
-       dev_warn(&chip->dev,
-                "AMD fTPM version 0x%llx causes system stutter; hwrng disabled\n",
-                version);
-
-       return true;
-}
-#else
-static inline bool tpm_amd_is_rng_defective(struct tpm_chip *chip)
-{
-       return false;
-}
-#endif /* CONFIG_X86 */
-
 static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 {
        struct tpm_chip *chip = container_of(rng, struct tpm_chip, hwrng);
@@ -585,7 +521,7 @@ static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 static int tpm_add_hwrng(struct tpm_chip *chip)
 {
        if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM) || tpm_is_firmware_upgrade(chip) ||
-           tpm_amd_is_rng_defective(chip))
+           chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED)
                return 0;
 
        snprintf(chip->hwrng_name, sizeof(chip->hwrng_name),
@@ -716,7 +652,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
 {
        tpm_del_legacy_sysfs(chip);
        if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip) &&
-           !tpm_amd_is_rng_defective(chip))
+           !(chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED))
                hwrng_unregister(&chip->hwrng);
        tpm_bios_log_teardown(chip);
        if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index cbbedf52607c08da175082f37ae7005bc5917898..7f7f3bded4535787ec6015f2e584044f79a9a5d1 100644 (file)
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -463,6 +463,28 @@ static bool crb_req_canceled(struct tpm_chip *chip, u8 status)
        return (cancel & CRB_CANCEL_INVOKE) == CRB_CANCEL_INVOKE;
 }
 
+static int crb_check_flags(struct tpm_chip *chip)
+{
+       u32 val;
+       int ret;
+
+       ret = crb_request_locality(chip, 0);
+       if (ret)
+               return ret;
+
+       ret = tpm2_get_tpm_pt(chip, TPM2_PT_MANUFACTURER, &val, NULL);
+       if (ret)
+               goto release;
+
+       if (val == 0x414D4400U /* AMD */)
+               chip->flags |= TPM_CHIP_FLAG_HWRNG_DISABLED;
+
+release:
+       crb_relinquish_locality(chip, 0);
+
+       return ret;
+}
+
 static const struct tpm_class_ops tpm_crb = {
        .flags = TPM_OPS_AUTO_STARTUP,
        .status = crb_status,
@@ -800,6 +822,14 @@ static int crb_acpi_add(struct acpi_device *device)
        chip->acpi_dev_handle = device->handle;
        chip->flags = TPM_CHIP_FLAG_TPM2;
 
+       rc = tpm_chip_bootstrap(chip);
+       if (rc)
+               goto out;
+
+       rc = crb_check_flags(chip);
+       if (rc)
+               goto out;
+
        rc = tpm_chip_register(chip);
 
 out:

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 4e22e4f4cec85341d2b4c10a613ecaefecf909fe..df5cd4245f29956af5d01f3b62a6a1c2aebbaed3 100644 (file)
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -282,6 +282,7 @@ enum tpm_chip_flags {
        TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED    = BIT(6),
        TPM_CHIP_FLAG_FIRMWARE_UPGRADE          = BIT(7),
        TPM_CHIP_FLAG_SUSPENDED                 = BIT(8),
+       TPM_CHIP_FLAG_HWRNG_DISABLED            = BIT(9),
 };
 
 #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)