linux-kernel - Re: [PATCH v3 07/10] tpm-buf: check for corruption in tpm_buf_append

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Message-ID: <aNu7R8J8h8Kmon0H@earth.li>
Date: Tue, 30 Sep 2025 12:13:11 +0100
From: Jonathan McDowell <noodles@...th.li>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-integrity@...r.kernel.org, dpsmith@...rtussolutions.com,
	ross.philipson@...cle.com,
	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>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Mimi Zohar <zohar@...ux.ibm.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 v3 07/10] tpm-buf: check for corruption in
 tpm_buf_append_handle()

On Mon, Sep 29, 2025 at 10:48:29PM +0300, Jarkko Sakkinen wrote:
> From: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
> 
> Unify TPM_BUF_BOUNDARY_ERROR and TPM_BUF_OVERFLOW into TPM_BUF_INVALID
> flag because semantically they are identical.
> 
> Test and set TPM_BUF_INVALID in tpm_buf_append_handle() following the
> pattern from other functions in tpm-buf.c.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>

Reviewed-by: Jonathan McDowell <noodles@...a.com>

> ---
> v3:
> - No changes.
> v2:
> - A new patch.
> ---
>  drivers/char/tpm/tpm-buf.c                | 14 ++++++++------
>  include/linux/tpm.h                       |  8 +++-----
>  security/keys/trusted-keys/trusted_tpm2.c |  6 +++---
>  3 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index dc882fc9fa9e..69ee77400539 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -104,13 +104,12 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
>   */
>  void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
>  {
> -	/* Return silently if overflow has already happened. */
> -	if (buf->flags & TPM_BUF_OVERFLOW)
> +	if (buf->flags & TPM_BUF_INVALID)
>  		return;
>  
>  	if ((buf->length + new_length) > PAGE_SIZE) {
>  		WARN(1, "tpm_buf: write overflow\n");
> -		buf->flags |= TPM_BUF_OVERFLOW;
> +		buf->flags |= TPM_BUF_INVALID;
>  		return;
>  	}
>  
> @@ -157,8 +156,12 @@ EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
>   */
>  void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle)
>  {
> +	if (buf->flags & TPM_BUF_INVALID)
> +		return;
> +
>  	if (buf->flags & TPM_BUF_TPM2B) {
>  		dev_err(&chip->dev, "Invalid buffer type (TPM2B)\n");
> +		buf->flags |= TPM_BUF_INVALID;
>  		return;
>  	}
>  
> @@ -177,14 +180,13 @@ static void tpm_buf_read(struct tpm_buf *buf, off_t *offset, size_t count, void
>  {
>  	off_t next_offset;
>  
> -	/* Return silently if overflow has already happened. */
> -	if (buf->flags & TPM_BUF_BOUNDARY_ERROR)
> +	if (buf->flags & TPM_BUF_INVALID)
>  		return;
>  
>  	next_offset = *offset + count;
>  	if (next_offset > buf->length) {
>  		WARN(1, "tpm_buf: read out of boundary\n");
> -		buf->flags |= TPM_BUF_BOUNDARY_ERROR;
> +		buf->flags |= TPM_BUF_INVALID;
>  		return;
>  	}
>  
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index e72e7657faa2..5283f32781c4 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -366,12 +366,10 @@ struct tpm_header {
>  } __packed;
>  
>  enum tpm_buf_flags {
> -	/* the capacity exceeded: */
> -	TPM_BUF_OVERFLOW	= BIT(0),
>  	/* TPM2B format: */
> -	TPM_BUF_TPM2B		= BIT(1),
> -	/* read out of boundary: */
> -	TPM_BUF_BOUNDARY_ERROR	= BIT(2),
> +	TPM_BUF_TPM2B		= BIT(0),
> +	/* The buffer is in invalid and unusable state: */
> +	TPM_BUF_INVALID		= BIT(1),
>  };
>  
>  /*
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 8e3b283a59b2..119d5152c0db 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -295,7 +295,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  	/* creation PCR */
>  	tpm_buf_append_u32(&buf, 0);
>  
> -	if (buf.flags & TPM_BUF_OVERFLOW) {
> +	if (buf.flags & TPM_BUF_INVALID) {
>  		rc = -E2BIG;
>  		tpm2_end_auth_session(chip);
>  		goto out;
> @@ -308,7 +308,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  		goto out;
>  
>  	blob_len = tpm_buf_read_u32(&buf, &offset);
> -	if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_BOUNDARY_ERROR) {
> +	if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_INVALID) {
>  		rc = -E2BIG;
>  		goto out;
>  	}
> @@ -414,7 +414,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  
>  	tpm_buf_append(&buf, blob, blob_len);
>  
> -	if (buf.flags & TPM_BUF_OVERFLOW) {
> +	if (buf.flags & TPM_BUF_INVALID) {
>  		rc = -E2BIG;
>  		tpm2_end_auth_session(chip);
>  		goto out;
> -- 
> 2.39.5
> 
> 

J.

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