6.11-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
commit 9265fed6db601ee2ec47577815387458ef4f047a upstream.
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@xxxxxxxxxxxxxxx # v6.4+
Fixes: 99d464506255 ("tpm: Prevent hwrng from activating during resume")
Reported-by: Mike Seo <mikeseohyungjin@xxxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219383
Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
Tested-by: Mike Seo <mikeseohyungjin@xxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/tpm/tpm-chip.c | 4 ----
drivers/char/tpm/tpm-interface.c | 32 ++++++++++++++++++++++----------
2 files changed, 22 insertions(+), 14 deletions(-)
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -525,10 +525,6 @@ static int tpm_hwrng_read(struct 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);
}
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -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
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;
}
