linux-kernel - Re: [PATCH v10 4/4] tpm_vpm_proxy: Use stack for TPM_CC_SET

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Message-ID: <swkdunznhlk5atrdfsiud57uzcvkmknnarzfh6esq3xzy74tmk@2qqsv6tvdtlw>
Date: Mon, 22 Sep 2025 10:46:36 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-integrity@...r.kernel.org, 
	Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>, 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 v10 4/4] tpm_vpm_proxy: Use stack for TPM_CC_SET_LOCALITY

On Sun, Sep 21, 2025 at 05:08:04AM +0300, Jarkko Sakkinen wrote:
>From: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
>
>Use stack allocation for TPM_CC_SET_LOCALITY, as it has known fixed size.
>
>Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
>---
> drivers/char/tpm/tpm1-cmd.c       |  2 +-
> drivers/char/tpm/tpm_vtpm_proxy.c | 12 +++++-------
> 2 files changed, 6 insertions(+), 8 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
>index 11c16ad9b2a7..433908cfb4a9 100644
>--- a/drivers/char/tpm/tpm1-cmd.c
>+++ b/drivers/char/tpm/tpm1-cmd.c
>@@ -328,7 +328,7 @@ static int tpm1_startup(struct tpm_chip *chip)
> 	int rc;
>
> 	dev_info(&chip->dev, "TPM_Startup\n");
>-	tpm_buf_init(buf, TPM_BUF_INT_SIZE);
>+	tpm_buf_init(buf, TPM_BUF_MIN_SIZE);

This change should be squashed in patch 2, right?

Thanks,
Stefano

> 	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
> 	tpm_buf_append_u16(buf, TPM_ST_CLEAR);
> 	rc = tpm_transmit_cmd(chip, buf, 0, "TPM_Startup");
>diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
>index e5de14379eb2..0f1b1b67ed4e 100644
>--- a/drivers/char/tpm/tpm_vtpm_proxy.c
>+++ b/drivers/char/tpm/tpm_vtpm_proxy.c
>@@ -395,15 +395,13 @@ static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
>
> static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
> {
>-	int rc;
>-	const struct tpm_header *header;
> 	struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
>+	u8 buf_data[TPM_BUF_MIN_SIZE];
>+	struct tpm_buf *buf = (struct tpm_buf *)buf_data;
>+	const struct tpm_header *header;
>+	int rc;
>
>-	struct tpm_buf *buf __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
>-	if (!buf)
>-		return -ENOMEM;
>-
>-	tpm_buf_init(buf, TPM_BUF_MAX_SIZE);
>+	tpm_buf_init(buf, TPM_BUF_MIN_SIZE);
> 	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> 		tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_SET_LOCALITY);
> 	else
>-- 
>2.39.5
>