On Sat, Jul 18, 2026 at 09:39:35PM +0300, Jarkko Sakkinen wrote:
> On Wed, Jul 15, 2026 at 06:03:55PM -0600, Ivy Lopez wrote:
> > The context_buf and session_buf fields in struct tpm_space contain
> > TPM context blobs which may include sensitive cryptographic material.
> > Use kfree_sensitive() instead of kfree() to ensure the memory is
> > zeroed before being freed, consistent with how chip->auth is handled
> > in the same tpm_dev_release() function since commit c424d2664f08
> > ("tpm: Use kfree_sensitive() to free auth session in tpm_dev_release()")
> >
> > Signed-off-by: Ivy Lopez <[email protected]>
> > ---
> > drivers/char/tpm/tpm-chip.c | 4 ++--
> > drivers/char/tpm/tpm2-space.c | 6 +++---
> > 2 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 12b7394b34bd..6f16fc358175 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -244,8 +244,8 @@ static void tpm_dev_release(struct device *dev)
> > idr_remove(&dev_nums_idr, chip->dev_num);
> > mutex_unlock(&idr_lock);
> >
> > - kfree(chip->work_space.context_buf);
> > - kfree(chip->work_space.session_buf);
> > + kfree_sensitive(chip->work_space.context_buf);
> > + kfree_sensitive(chip->work_space.session_buf);
> > #ifdef CONFIG_TCG_TPM2_HMAC
> > kfree_sensitive(chip->auth);
> > #endif
> > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> > index 60354cd53b5c..a7200e6dc462 100644
> > --- a/drivers/char/tpm/tpm2-space.c
> > +++ b/drivers/char/tpm/tpm2-space.c
> > @@ -46,7 +46,7 @@ int tpm2_init_space(struct tpm_space *space, unsigned int
> > buf_size)
> >
> > space->session_buf = kzalloc(buf_size, GFP_KERNEL);
> > if (space->session_buf == NULL) {
> > - kfree(space->context_buf);
> > + kfree_sensitive(space->context_buf);
> > /* Prevent caller getting a dangling pointer. */
> > space->context_buf = NULL;
> > return -ENOMEM;
> > @@ -64,8 +64,8 @@ void tpm2_del_space(struct tpm_chip *chip, struct
> > tpm_space *space)
> > tpm_put_ops(chip);
> > }
> >
> > - kfree(space->context_buf);
> > - kfree(space->session_buf);
> > + kfree_sensitive(space->context_buf);
> > + kfree_sensitive(space->session_buf);
> > }
> >
> > int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
> > --
> > 2.55.0
> >
>
> Yep, as James said, there's no plain text to uncover.
And also tied to power cycle.
BR, Jarkko
