This is a note to let you know that I've just added the patch titled
tpm: fix potential NULL pointer access in tpm_del_char_device
to the 5.16-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-fix-potential-null-pointer-access-in-tpm_del_char_device.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From eabad7ba2c752392ae50f24a795093fb115b686d Mon Sep 17 00:00:00 2001
From: Lino Sanfilippo <LinoSanfilippo@xxxxxx>
Date: Mon, 20 Dec 2021 16:06:35 +0100
Subject: tpm: fix potential NULL pointer access in tpm_del_char_device
From: Lino Sanfilippo <LinoSanfilippo@xxxxxx>
commit eabad7ba2c752392ae50f24a795093fb115b686d upstream.
Some SPI controller drivers unregister the controller in the shutdown
handler (e.g. BCM2835). If such a controller is used with a TPM 2 slave
chip->ops may be accessed when it is already NULL:
At system shutdown the pre-shutdown handler tpm_class_shutdown() shuts down
TPM 2 and sets chip->ops to NULL. Then at SPI controller unregistration
tpm_tis_spi_remove() is called and eventually calls tpm_del_char_device()
which tries to shut down TPM 2 again. Thereby it accesses chip->ops again:
(tpm_del_char_device calls tpm_chip_start which calls tpm_clk_enable which
calls chip->ops->clk_enable).
Avoid the NULL pointer access by testing if chip->ops is valid and skipping
the TPM 2 shutdown procedure in case it is NULL.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@xxxxxx>
Fixes: 39d0099f9439 ("powerpc/pseries: Add shutdown() to vio_driver and vio_bus")
Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Tested-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/tpm/tpm-chip.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -474,13 +474,21 @@ static void tpm_del_char_device(struct t
/* Make the driver uncallable. */
down_write(&chip->ops_sem);
- if (chip->flags & TPM_CHIP_FLAG_TPM2) {
- if (!tpm_chip_start(chip)) {
- tpm2_shutdown(chip, TPM2_SU_CLEAR);
- tpm_chip_stop(chip);
+
+ /*
+ * Check if chip->ops is still valid: In case that the controller
+ * drivers shutdown handler unregisters the controller in its
+ * shutdown handler we are called twice and chip->ops to NULL.
+ */
+ if (chip->ops) {
+ if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+ if (!tpm_chip_start(chip)) {
+ tpm2_shutdown(chip, TPM2_SU_CLEAR);
+ tpm_chip_stop(chip);
+ }
}
+ chip->ops = NULL;
}
- chip->ops = NULL;
up_write(&chip->ops_sem);
}
Patches currently in stable-queue which might be from LinoSanfilippo@xxxxxx are
queue-5.16/tpm-fix-potential-null-pointer-access-in-tpm_del_char_device.patch
queue-5.16/serial-amba-pl011-do-not-request-memory-region-twice.patch
