On 12/20/21 10:06, Lino Sanfilippo wrote:
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. Fixes: dcbeab1946454 ("tpm: fix crash in tpm_tis deinitialization") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Lino Sanfilippo <LinoSanfilippo@xxxxxx> --- Changes to v2: - rephrased the commit message to clarify the circumstances under which this bug triggers (as requested by Jarkko) I was able to reproduce this issue with a SLB 9670 TPM chip controlled by a BCM2835 SPI controller. The approach to fix this issue in the BCM2835 driver was rejected after a discussion on the mailing list: https://marc.info/?l=linux-integrity&m=163285906725367&w=2 The reason for the rejection was the realization, that this issue should rather be fixed in the TPM code: https://marc.info/?l=linux-spi&m=163311087423271&w=2 So this is the reworked version of a patch that is supposed to do that. drivers/char/tpm/tpm-chip.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c index ddaeceb7e109..7960da490e72 100644 --- a/drivers/char/tpm/tpm-chip.c +++ b/drivers/char/tpm/tpm-chip.c @@ -474,13 +474,19 @@ static void tpm_del_char_device(struct tpm_chip *chip)/* 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); }base-commit: a7904a538933c525096ca2ccde1e60d0ee62c08e
Fixes: 39d0099f9439 ("powerpc/pseries: Add shutdown() to vio_driver and vio_bus")
Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx> Tested-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
