On Wed, Apr 26, 2023 at 08:29:28PM +0300, Jarkko Sakkinen wrote:

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: 6e592a065d51 ("tpm: Move Linux RNG connection to hwrng") Signed-off-by: Jarkko Sakkinen jarkko@kernel.org

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com

---

drivers/char/tpm/tpm-chip.c | 4 ++++ drivers/char/tpm/tpm-interface.c | 10 ++++++++++ include/linux/tpm.h | 13 +++++++------ 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c index 6fdfa65a00c3..6f5ee27aeda1 100644 --- a/drivers/char/tpm/tpm-chip.c +++ b/drivers/char/tpm/tpm-chip.c @@ -572,6 +572,10 @@ 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 4dc97b9f65fb..d7073dc45444 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -274,13 +274,14 @@ enum tpm2_cc_attrs { #define TPM_VID_ATML 0x1114 enum tpm_chip_flags {

• TPM_CHIP_FLAG_TPM2 = BIT(1),
• TPM_CHIP_FLAG_IRQ = BIT(2),
• TPM_CHIP_FLAG_VIRTUAL = BIT(3),
• TPM_CHIP_FLAG_HAVE_TIMEOUTS = BIT(4),
• TPM_CHIP_FLAG_ALWAYS_POWERED = BIT(5),

• TPM_CHIP_FLAG_SUSPENDED = BIT(0),
• TPM_CHIP_FLAG_TPM2 = BIT(1),
• TPM_CHIP_FLAG_IRQ = BIT(2),
• TPM_CHIP_FLAG_VIRTUAL = BIT(3),
• TPM_CHIP_FLAG_HAVE_TIMEOUTS = BIT(4),
• 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_FIRMWARE_UPGRADE = BIT(7),

};

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

2.39.2