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FAILED: patch "[PATCH] tpm: Lock TPM chip in tpm_pm_suspend() first" failed to apply to 6.6-stable tree

PATCH [email protected] 1 participant 1 message Nov 9, 2024

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Stable branch TPM device driver
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The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 9265fed6db601ee2ec47577815387458ef4f047a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024110926-shortness-stark-e2ea@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9265fed6db601ee2ec47577815387458ef4f047a Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <[email protected]>
Date: Thu, 31 Oct 2024 02:16:09 +0200
Subject: [PATCH] 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 [email protected] # v6.4+
Fixes 99d464506255 ("tpm: Prevent hwrng from activating during resume")
Reported-by Mike Seo <[email protected]>
Closes https://bugzilla.kernel.org/show_bug.cgi?id=219383
Reviewed-by Jerry Snitselaar <[email protected]>
Tested-by Mike Seo <[email protected]>
Signed-off-by Jarkko Sakkinen <[email protected]>
drivers/char/tpm/tpm-chip.c +0 -4
index 1ff99a7091bb..7df7abaf3e52 100644
@@ -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);
 }
drivers/char/tpm/tpm-interface.c +22 -10
index 8134f002b121..b1daa0d7b341 100644
@@ -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;
 }