FAILED: patch "[PATCH] tpm: Prevent hwrng from activating during resume" failed to apply to 6.3-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.3-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 <stable@vger.kernel.org>.

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-6.3.y
git checkout FETCH_HEAD
git cherry-pick -x 99d46450625590d410f86fe4660a5eff7d3b8343
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023052257-oppose-sculpture-982a@gregkh' --subject-prefix 'PATCH 6.3.y' HEAD^..

Possible dependencies:

99d464506255 ("tpm: Prevent hwrng from activating during resume")
0c8862de05c1 ("tpm: Re-enable TPM chip boostrapping non-tpm_tis TPM drivers")
548eb516ec0f ("tpm, tpm_tis: startup chip before testing for interrupts")

thanks,

greg k-h

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

From 99d46450625590d410f86fe4660a5eff7d3b8343 Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko@kernel.org>
Date: Wed, 26 Apr 2023 20:29:28 +0300
Subject: [PATCH] tpm: Prevent hwrng from activating during resume

Set TPM_CHIP_FLAG_SUSPENDED in tpm_pm_suspend() and reset in
tpm_pm_resume(). While the flag is set, tpm_hwrng() gives back zero
bytes. This prevents hwrng from racing during resume.

Cc: stable@vger.kernel.org
Fixes: 6e592a065d51 ("tpm: Move Linux RNG connection to hwrng")
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.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 c10a4aa97373..cd48033b804a 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -571,6 +571,10 @@ 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 4463d0018290..586ca10b0d72 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -412,6 +412,8 @@ int tpm_pm_suspend(struct device *dev)
 	}
 
 suspended:
+	chip->flags |= TPM_CHIP_FLAG_SUSPENDED;
+
 	if (rc)
 		dev_err(dev, "Ignoring error %d while suspending\n", rc);
 	return 0;
@@ -429,6 +431,14 @@ int tpm_pm_resume(struct device *dev)
 	if (chip == NULL)
 		return -ENODEV;
 
+	chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED;
+
+	/*
+	 * Guarantee that SUSPENDED is written last, so that hwrng does not
+	 * activate before the chip has been fully resumed.
+	 */
+	wmb();
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_pm_resume);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 77693389c3f9..6a1e8f157255 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -282,6 +282,7 @@ enum tpm_chip_flags {
 	TPM_CHIP_FLAG_ALWAYS_POWERED		= BIT(5),
 	TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED	= BIT(6),
 	TPM_CHIP_FLAG_FIRMWARE_UPGRADE		= BIT(7),
+	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
 };
 
 #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)