Re: [PATCH v2] keys/trusted_keys: reuse TPM version in option handling

[Jarkko Sakkinen <jarkko.sakkinen@iki.fi>]

On Fri, Oct 02, 2026 at 12:40:50PM +0530, Srish Srinivasan wrote:
> Determine the TPM version once in the seal and unseal paths and reuse it
> when allocating and parsing trusted key options. This avoids redundant TPM
> version checks.

So this is a bit nitpicking perhaps but a patch that would just clean
the code up a bit would not be be worth of applying. Almost anything
that "does nothing" goes to that bin.

What I'm saying is that the conclusion in the last sentence goes to
wrong direction but luckily the change has also feasible effects that
we care about.

By caching tpm_is_tpm2() there are less fallible sites in the key
creation process, and reduced number of roundtrips with the TPM chip.

Or from blackbox perspective it reduces I/O traffic between kernel
and the hardware platform.

> 
> Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
> Changelog:
> 
>  v2:
>   - Use bool to indicate whether the chip is TPM 2.0 in the option helpers
> 
>  security/keys/trusted-keys/trusted_tpm1.c | 35 +++++++++--------------
>  1 file changed, 13 insertions(+), 22 deletions(-)
> 
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index 3ec078ca3f97..6dbce058368f 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -700,7 +700,7 @@ static const match_table_t key_tokens = {
>  
>  /* can have zero or more token= options */
>  static int getoptions(char *c, struct trusted_key_payload *pay,
> -		      struct trusted_key_options *opt)
> +		      struct trusted_key_options *opt, bool is_tpm2)
>  {
>  	struct trusted_key_tpm *private = opt->private;
>  	substring_t args[MAX_OPT_ARGS];
> @@ -712,13 +712,8 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  	unsigned long token_mask = 0;
>  	unsigned int digest_len;
>  	int i;
> -	int tpm2;
> -
> -	tpm2 = tpm_is_tpm2(chip);
> -	if (tpm2 < 0)
> -		return tpm2;
>  
> -	private->hash = tpm2 ? HASH_ALGO_SHA256 : HASH_ALGO_SHA1;
> +	private->hash = is_tpm2 ? HASH_ALGO_SHA256 : HASH_ALGO_SHA1;
>  
>  	if (!c)
>  		return 0;
> @@ -773,7 +768,7 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  				break;
>  			}
>  
> -			if (tpm2 &&
> +			if (is_tpm2 &&
>  			    private->blobauth_len <=
>  			    sizeof(private->blobauth)) {
>  				memcpy(private->blobauth, args[0].from,
> @@ -808,14 +803,15 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  			}
>  			if (i == HASH_ALGO__LAST)
>  				return -EINVAL;
> -			if  (!tpm2 && i != HASH_ALGO_SHA1) {
> +			if (!is_tpm2 && i != HASH_ALGO_SHA1) {
>  				pr_info("TPM 1.x only supports SHA-1.\n");
>  				return -EINVAL;
>  			}
>  			break;
>  		case Opt_policydigest:
>  			digest_len = hash_digest_size[private->hash];
> -			if (!tpm2 || strlen(args[0].from) != (2 * digest_len))
> +			if (!is_tpm2 ||
> +			    strlen(args[0].from) != (2 * digest_len))
>  				return -EINVAL;
>  			res = hex2bin(private->policydigest, args[0].from,
>  				      digest_len);
> @@ -824,7 +820,7 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  			private->policydigest_len = digest_len;
>  			break;
>  		case Opt_policyhandle:
> -			if (!tpm2)
> +			if (!is_tpm2)
>  				return -EINVAL;
>  			res = kstrtoul(args[0].from, 16, &handle);
>  			if (res < 0)
> @@ -838,15 +834,10 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
>  	return 0;
>  }
>  
> -static struct trusted_key_options *trusted_options_alloc(void)
> +static struct trusted_key_options *trusted_options_alloc(bool is_tpm2)
>  {
>  	struct trusted_key_tpm *private;
>  	struct trusted_key_options *options;
> -	int tpm2;
> -
> -	tpm2 = tpm_is_tpm2(chip);
> -	if (tpm2 < 0)
> -		return NULL;
>  
>  	options = kzalloc_obj(*options);
>  	if (options) {
> @@ -858,7 +849,7 @@ static struct trusted_key_options *trusted_options_alloc(void)
>  			kfree_sensitive(options);
>  			options = NULL;
>  		} else {
> -			if (!tpm2)
> +			if (!is_tpm2)
>  				private->keyhandle = SRKHANDLE;
>  			options->private = private;
>  		}
> @@ -877,13 +868,13 @@ static int trusted_tpm_seal(struct trusted_key_payload *p, char *datablob)
>  	if (tpm2 < 0)
>  		return tpm2;
>  
> -	options = trusted_options_alloc();
> +	options = trusted_options_alloc(tpm2);
>  	if (!options)
>  		return -ENOMEM;
>  
>  	private = options->private;
>  
> -	ret = getoptions(datablob, p, options);
> +	ret = getoptions(datablob, p, options, tpm2);
>  	if (ret < 0)
>  		return ret;
>  	dump_options(options);
> @@ -922,12 +913,12 @@ static int trusted_tpm_unseal(struct trusted_key_payload *p, char *datablob)
>  	if (tpm2 < 0)
>  		return tpm2;
>  
> -	options = trusted_options_alloc();
> +	options = trusted_options_alloc(tpm2);
>  	if (!options)
>  		return -ENOMEM;
>  	private = options->private;
>  
> -	ret = getoptions(datablob, p, options);
> +	ret = getoptions(datablob, p, options, tpm2);
>  	if (ret < 0)
>  		return ret;
>  	dump_options(options);
> -- 
> 2.53.0
> 

Br, Jarkko