Commit 9265fed6db60 for kernel

commit 9265fed6db601ee2ec47577815387458ef4f047a
Author: Jarkko Sakkinen <jarkko@kernel.org>
Date:   Thu Oct 31 02:16:09 2024 +0200

    tpm: Lock TPM chip in tpm_pm_suspend() first

    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: 99d464506255 ("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>

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 1ff99a7091bb..7df7abaf3e52 100644
--- 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 *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 8134f002b121..b1daa0d7b341 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;

@@ -377,21 +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;
 }