This is a note to let you know that I've just added the patch titled
tpm: Prevent hwrng from activating during resume
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tpm-prevent-hwrng-from-activating-during-resume.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit de5046897a02437941da794b1fc27e7059f7aa16
Author: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Date: Wed Apr 26 20:29:28 2023 +0300
tpm: Prevent hwrng from activating during resume
[ Upstream commit 99d46450625590d410f86fe4660a5eff7d3b8343 ]
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@xxxxxxxxxxxxxxx
Fixes: 6e592a065d51 ("tpm: Move Linux RNG connection to hwrng")
Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 9c0a6aad81140..5be91591cb3b2 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -572,6 +572,10 @@ 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 7e513b7718320..0f941cb32eb17 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 77693389c3f9a..6a1e8f1572551 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)
