Hi, the patch below should also fix the issue that Stefan reported here: https://marc.info/?l=linux-integrity&m=163927245509564&w=2 Regards, Lino On 20.12.21 at 16:06, 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 >
