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tpm: Lock TPM chip in tpm_pm_suspend() first

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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: 99d4645062 ("tpm: Prevent hwrng from activating during resume")
Reported-by: Mike Seo <mikeseohyungjin@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219383
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Tested-by: Mike Seo <mikeseohyungjin@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Jarkko Sakkinen 2024-10-31 02:16:09 +02:00
parent 11066801dd
commit 9265fed6db
2 changed files with 22 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/char/tpm/tpm-chip.c
View File

@ -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);
}

32
drivers/char/tpm/tpm-interface.c
View File

@ -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);
}
tpm_put_ops(chip);
if (chip->flags & TPM_CHIP_FLAG_TPM2) {
tpm2_end_auth_session(chip);
tpm2_shutdown(chip, TPM2_SU_STATE);
goto suspended;
}
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;
}