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tpm: Prevent hwrng from activating during resume

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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: 6e592a065d ("tpm: Move Linux RNG connection to hwrng")
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Jarkko Sakkinen 2023-04-26 20:29:28 +03:00
parent 1398aa803f
commit 99d4645062
3 changed files with 15 additions and 0 deletions
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4
drivers/char/tpm/tpm-chip.c
View file

@ -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); 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); return tpm_get_random(chip, data, max);
} }

10
drivers/char/tpm/tpm-interface.c
View file

@ -412,6 +412,8 @@ int tpm_pm_suspend(struct device *dev)
} }
suspended: suspended:
chip->flags |= TPM_CHIP_FLAG_SUSPENDED;
if (rc) if (rc)
dev_err(dev, "Ignoring error %d while suspending\n", rc); dev_err(dev, "Ignoring error %d while suspending\n", rc);
return 0; return 0;
@ -429,6 +431,14 @@ int tpm_pm_resume(struct device *dev)
if (chip == NULL) if (chip == NULL)
return -ENODEV; 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; return 0;
} }
EXPORT_SYMBOL_GPL(tpm_pm_resume); EXPORT_SYMBOL_GPL(tpm_pm_resume);

1
include/linux/tpm.h
View file

@ -282,6 +282,7 @@ enum tpm_chip_flags {
TPM_CHIP_FLAG_ALWAYS_POWERED = BIT(5), TPM_CHIP_FLAG_ALWAYS_POWERED = BIT(5),
TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED = BIT(6), TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED = BIT(6),
TPM_CHIP_FLAG_FIRMWARE_UPGRADE = BIT(7), 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) #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)