commit 99d46450625590d410f86fe4660a5eff7d3b8343 upstream.
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 # v6.1+ Fixes: 6e592a065d51 ("tpm: Move Linux RNG connection to hwrng") Reviewed-by: Jerry Snitselaar jsnitsel@redhat.com Signed-off-by: Jarkko Sakkinen jarkko@kernel.org --- drivers/char/tpm/tpm-chip.c | 4 ++++ drivers/char/tpm/tpm-interface.c | 10 ++++++++++ include/linux/tpm.h | 1 + 3 files changed, 15 insertions(+)
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c index 5165f6d3da22..5e6d849c64ee 100644 --- a/drivers/char/tpm/tpm-chip.c +++ b/drivers/char/tpm/tpm-chip.c @@ -568,6 +568,10 @@ 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); }
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index 7e513b771832..0f941cb32eb1 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -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); diff --git a/include/linux/tpm.h b/include/linux/tpm.h index dfeb25a0362d..1fc953fa4158 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -280,6 +280,7 @@ 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)