From: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> commit fb5abce6b2bb5cb3d628aaa63fa821da8c4600f9 upstream. As part of the series conversion to remove nested TPM operations: https://lore.kernel.org/all/20190205224723.19671-1-jarkko.sakkinen@xxxxxxxxxxxxxxx/ exposure of the chip->tpm_mutex was removed from much of the upper level code. In this conversion, tpm2_del_space() was missed. This didn't matter much because it's usually called closely after a converted operation, so there's only a very tiny race window where the chip can be removed before the space flushing is done which causes a NULL deref on the mutex. However, there are reports of this window being hit in practice, so fix this by converting tpm2_del_space() to use tpm_try_get_ops(), which performs all the teardown checks before acquring the mutex. Cc: stable@xxxxxxxxxxxxxxx # 5.4.x Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/char/tpm/tpm2-space.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/drivers/char/tpm/tpm2-space.c +++ b/drivers/char/tpm/tpm2-space.c @@ -58,12 +58,12 @@ int tpm2_init_space(struct tpm_space *sp void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space) { - mutex_lock(&chip->tpm_mutex); - if (!tpm_chip_start(chip)) { + + if (tpm_try_get_ops(chip) == 0) { tpm2_flush_sessions(chip, space); - tpm_chip_stop(chip); + tpm_put_ops(chip); } - mutex_unlock(&chip->tpm_mutex); + kfree(space->context_buf); kfree(space->session_buf); }
