Setting TPM_CHIP_FLAG_SUSPENDED in the end of tpm_pm_suspend() can be racy
according to the bug report, as this leaves window for tpm_hwrng_read() to
be called while the operation is in progress.
To address this, lock the TPM chip before checking any possible flags.
This will guarantee that tpm_hwrng_read() and tpm_pm_suspend() won't
conflict with each other.
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
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
v2:
- Addressed my own remark:
https://lore.kernel.org/linux-integrity/D59JAI6RR2CD.G5E5T4ZCZ49W@xxxxxxxxxx/
---
drivers/char/tpm/tpm-interface.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 8134f002b121..e37fcf9361bc 100644
--- 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;
@@ -377,23 +384,22 @@ 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;
}
EXPORT_SYMBOL_GPL(tpm_pm_suspend);
--
2.47.0
