linux-kernel - Re: [PATCH v6 05/11] tpm2-sessions: Remove AUTH_MAX

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Message-ID: <b19c064b-9dfe-45d6-b23d-1bfaca6afb02@oracle.com>
Date: Mon, 12 Jan 2026 16:22:24 -0800
From: ross.philipson@...cle.com
To: Jarkko Sakkinen <jarkko@...nel.org>, linux-integrity@...r.kernel.org
Cc: Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
        David Howells <dhowells@...hat.com>, Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KEYS/KEYRINGS" <keyrings@...r.kernel.org>,
        "open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v6 05/11] tpm2-sessions: Remove AUTH_MAX_NAMES

On 12/14/25 7:38 AM, Jarkko Sakkinen wrote:
> In all of the call sites only one session is ever append. Thus, reduce
> AUTH_MAX_NAMES, which leads into removing constant completely.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
>   drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++--------------------
>   1 file changed, 11 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 3bc3c31cf512..37570dc088cf 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -72,9 +72,6 @@
>   #include <crypto/sha2.h>
>   #include <crypto/utils.h>
>   
> -/* maximum number of names the TPM must remember for authorization */
> -#define AUTH_MAX_NAMES	3
> -
>   #define AES_KEY_BYTES	AES_KEYSIZE_128
>   #define AES_KEY_BITS	(AES_KEY_BYTES*8)
>   
> @@ -136,8 +133,8 @@ struct tpm2_auth {
>   	 * handle, but they are part of the session by name, which
>   	 * we must compute and remember
>   	 */
> -	u8 name[AUTH_MAX_NAMES][TPM2_MAX_NAME_SIZE];
> -	u16 name_size_tbl[AUTH_MAX_NAMES];
> +	u8 name[TPM2_MAX_NAME_SIZE];
> +	u16 name_size;
>   };
>   
>   #ifdef CONFIG_TCG_TPM2_HMAC
> @@ -261,11 +258,14 @@ EXPORT_SYMBOL_GPL(tpm2_read_public);
>   int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
>   			u32 handle, u8 *name, u16 name_size)
>   {
> -#ifdef CONFIG_TCG_TPM2_HMAC

Removing CONFIG_TCG_TPM2_HMAC here causes a warning during compile since 
the auth variable is only used in the CONFIG_TCG_TPM2_HMAC block below.

Ross

>   	struct tpm2_auth *auth;
> -	int slot;
>   	int ret;
> -#endif
> +
> +	if (tpm_buf_length(buf) != TPM_HEADER_SIZE) {
> +		dev_err(&chip->dev, "too many handles\n");
> +		ret = -EIO;
> +		goto err;
> +	}
>   
>   	if (!tpm2_chip_auth(chip)) {
>   		tpm_buf_append_handle(chip, buf, handle);
> @@ -273,12 +273,6 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
>   	}
>   
>   #ifdef CONFIG_TCG_TPM2_HMAC
> -	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE) / 4;
> -	if (slot >= AUTH_MAX_NAMES) {
> -		dev_err(&chip->dev, "too many handles\n");
> -		ret = -EIO;
> -		goto err;
> -	}
>   	auth = chip->auth;
>   	if (auth->session != tpm_buf_length(buf)) {
>   		dev_err(&chip->dev, "session state malformed");
> @@ -287,16 +281,14 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
>   	}
>   	tpm_buf_append_u32(buf, handle);
>   	auth->session += 4;
> -	memcpy(auth->name[slot], name, name_size);
> -	auth->name_size_tbl[slot] = name_size;
> +	memcpy(auth->name, name, name_size);
> +	auth->name_size = name_size;
>   #endif
>   	return 0;
>   
> -#ifdef CONFIG_TCG_TPM2_HMAC
>   err:
>   	tpm2_end_auth_session(chip);
>   	return ret;
> -#endif
>   }
>   EXPORT_SYMBOL_GPL(tpm_buf_append_name);
>   
> @@ -665,8 +657,7 @@ int tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
>   	/* ordinal is already BE */
>   	sha256_update(&sctx, (u8 *)&head->ordinal, sizeof(head->ordinal));
>   	/* add the handle names */
> -	for (i = 0; i < handles; i++)
> -		sha256_update(&sctx, auth->name[i], auth->name_size_tbl[i]);
> +	sha256_update(&sctx, auth->name, auth->name_size);
>   	if (offset_s != tpm_buf_length(buf))
>   		sha256_update(&sctx, &buf->data[offset_s],
>   			      tpm_buf_length(buf) - offset_s);