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tpm: fix potential NULL pointer access in tpm_del_char_device 

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@vger.kernel.org
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Fixes: 39d0099f94 ("powerpc/pseries: Add shutdown() to vio_driver and vio_bus")
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Lino Sanfilippo 2021-12-20 16:06:35 +01:00 committed by Jarkko Sakkinen
parent 0aa698787a
commit eabad7ba2c
1 changed files with 13 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/char/tpm/tpm-chip.c
View File

@ -474,13 +474,21 @@ 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);
}