Commit 9265fed6 authored by Jarkko Sakkinen's avatar Jarkko Sakkinen
Browse files

tpm: Lock TPM chip in tpm_pm_suspend() first 



Setting TPM_CHIP_FLAG_SUSPENDED in the end of tpm_pm_suspend() can be racy
according, as this leaves window for tpm_hwrng_read() to be called while
the operation is in progress. The recent bug report gives also evidence of
this behaviour.

Aadress this by locking the TPM chip before checking any chip->flags both
in tpm_pm_suspend() and tpm_hwrng_read(). Move TPM_CHIP_FLAG_SUSPENDED
check inside tpm_get_random() so that it will be always checked only when
the lock is reserved.

Cc: stable@vger.kernel.org # v6.4+
Fixes: 99d46450 ("tpm: Prevent hwrng from activating during resume")
Reported-by: default avatarMike Seo <mikeseohyungjin@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219383


Reviewed-by: default avatarJerry Snitselaar <jsnitsel@redhat.com>
Tested-by: default avatarMike Seo <mikeseohyungjin@gmail.com>
Signed-off-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
parent 11066801

drivers/char/tpm/tpm-chip.c

+0 −4
Original line number Diff line number Diff line
@@ -525,10 +525,6 @@ 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);



	/* Give back zero bytes, as TPM chip has not yet fully resumed: */

	if (chip->flags & TPM_CHIP_FLAG_SUSPENDED)

		return 0;



	return tpm_get_random(chip, data, max);

}

drivers/char/tpm/tpm-interface.c

+22 −10
Original line number Diff line number Diff line
@@ -370,6 +370,13 @@ int tpm_pm_suspend(struct device *dev) 
	if (!chip)

		return -ENODEV;



	rc = tpm_try_get_ops(chip);

	if (rc) {

		/* Can be safely set out of locks, as no action cannot race: */

		chip->flags |= TPM_CHIP_FLAG_SUSPENDED;

		goto out;

	}



	if (chip->flags & TPM_CHIP_FLAG_ALWAYS_POWERED)

		goto suspended;
@@ -377,21 +384,19 @@ int tpm_pm_suspend(struct device *dev) 
	    !pm_suspend_via_firmware())

		goto suspended;



	rc = tpm_try_get_ops(chip);

	if (!rc) {

	if (chip->flags & TPM_CHIP_FLAG_TPM2) {

		tpm2_end_auth_session(chip);

		tpm2_shutdown(chip, TPM2_SU_STATE);

		} else {

			rc = tpm1_pm_suspend(chip, tpm_suspend_pcr);

		goto suspended;

	}



		tpm_put_ops(chip);

	}

	rc = tpm1_pm_suspend(chip, tpm_suspend_pcr);



suspended:

	chip->flags |= TPM_CHIP_FLAG_SUSPENDED;

	tpm_put_ops(chip);



out:

	if (rc)

		dev_err(dev, "Ignoring error %d while suspending\n", rc);

	return 0;
@@ -440,11 +445,18 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max) 
	if (!chip)

		return -ENODEV;



	/* Give back zero bytes, as TPM chip has not yet fully resumed: */

	if (chip->flags & TPM_CHIP_FLAG_SUSPENDED) {

		rc = 0;

		goto out;

	}



	if (chip->flags & TPM_CHIP_FLAG_TPM2)

		rc = tpm2_get_random(chip, out, max);

	else

		rc = tpm1_get_random(chip, out, max);



out:

	tpm_put_ops(chip);

	return rc;

}