On Mon, Mar 07, 2022 at 11:22:27AM -0500, James Bottomley wrote: > On Mon, 2022-03-07 at 17:41 +0200, Jarkko Sakkinen wrote: > [...] > > James, would it possible for you to construct a proper patch from > > this and send it so we could include it to the next PR (use my tree > > as baseline)? > > Sure, There's not really any identifiable patch for a fixes tag, since > the race really always existed. > > How about the below. > > James > > -------------------8>8>8><8<8<8------------------ > > From 3e0e640e47e5728b68693c5d45bf3cdd0bff48ca Mon Sep 17 00:00:00 2001 > From: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > Date: Mon, 7 Mar 2022 11:16:55 -0500 > Subject: [PATCH] tpm: use try_get_ops() in tpm-space.c > > 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. > > Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > --- > drivers/char/tpm/tpm2-space.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c > index 265ec72b1d81..ffb35f0154c1 100644 > --- 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 *space, unsigned int buf_size) > > 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); > } > -- > 2.34.1 > > Thank you! LGTM. Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> BR, Jarkko
