Commit 99d46450 authored by Jarkko Sakkinen's avatar Jarkko Sakkinen
Browse files

tpm: Prevent hwrng from activating during resume 



Set TPM_CHIP_FLAG_SUSPENDED in tpm_pm_suspend() and reset in
tpm_pm_resume(). While the flag is set, tpm_hwrng() gives back zero
bytes. This prevents hwrng from racing during resume.

Cc: stable@vger.kernel.org
Fixes: 6e592a06 ("tpm: Move Linux RNG connection to hwrng")
Reviewed-by: default avatarJerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
parent 1398aa80

drivers/char/tpm/tpm-chip.c

+4 −0
Original line number Diff line number Diff line
@@ -571,6 +571,10 @@ 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

+10 −0
Original line number Diff line number Diff line
@@ -412,6 +412,8 @@ int tpm_pm_suspend(struct device *dev) 
	}



suspended:

	chip->flags |= TPM_CHIP_FLAG_SUSPENDED;



	if (rc)

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

	return 0;
@@ -429,6 +431,14 @@ int tpm_pm_resume(struct device *dev) 
	if (chip == NULL)

		return -ENODEV;



	chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED;



	/*

	 * Guarantee that SUSPENDED is written last, so that hwrng does not

	 * activate before the chip has been fully resumed.

	 */

	wmb();



	return 0;

}

EXPORT_SYMBOL_GPL(tpm_pm_resume);

include/linux/tpm.h

+1 −0
Original line number Diff line number Diff line
@@ -282,6 +282,7 @@ enum tpm_chip_flags { 
	TPM_CHIP_FLAG_ALWAYS_POWERED		= BIT(5),

	TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED	= BIT(6),

	TPM_CHIP_FLAG_FIRMWARE_UPGRADE		= BIT(7),

	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),

};



#define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)