On Thu, Apr 09, 2026 at 05:20:54PM +0000, Gunnar Kudrjavets wrote:
> tpm_dev_release() uses plain kfree() to free chip->auth, which contains
> sensitive cryptographic material including HMAC session keys, nonces,
> and passphrase data (struct tpm2_auth).
>
> Every other code path that frees this structure uses kfree_sensitive()
> to zero the memory before releasing it: both tpm2_end_auth_session()
> and tpm_buf_check_hmac_response() do so. The tpm_dev_release() path
> is the only one that does not, leaving key material in freed slab
> memory until it is eventually overwritten.
>
> Use kfree_sensitive() for consistency with the rest of the driver and
> to ensure session keys are scrubbed during device teardown.
>
> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> Signed-off-by: Gunnar Kudrjavets <[email protected]>
> Reviewed-by: Justinien Bouron <[email protected]>
> ---
> drivers/char/tpm/tpm-chip.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 082b910ddf0d..17d9d71774ec 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -247,7 +247,7 @@ static void tpm_dev_release(struct device *dev)
> kfree(chip->work_space.context_buf);
> kfree(chip->work_space.session_buf);
> #ifdef CONFIG_TCG_TPM2_HMAC
> - kfree(chip->auth);
> + kfree_sensitive(chip->auth);
> #endif
> kfree(chip);
> }
>
> base-commit: 03e5553f5fb99cb47c315e167a604a9c69e6f724
> --
> 2.47.3
>
Applied.
Reviewed-by: Jarkko Sakkinen <[email protected]>
BR, Jarkko
