As part of the series conversion to remove nested TPM operations:
https://lore.kernel.org/all/[email protected]/
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 <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
---
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
On Mon, Mar 07, 2022 at 03:58:03PM -0500, James Bottomley wrote:
> As part of the series conversion to remove nested TPM operations:
>
> https://lore.kernel.org/all/[email protected]/
>
> 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 <[email protected]>
> Reviewed-by: Jarkko Sakkinen <[email protected]>
> ---
> 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!
BR, Jarkko