Re: [PATCH v3 07/10] tpm-buf: check for corruption in tpm_buf_append_handle()

[Jarkko Sakkinen <jarkko@kernel.org>]

On Tue, Sep 30, 2025 at 12:13:11PM +0100, Jonathan McDowell wrote:
> On Mon, Sep 29, 2025 at 10:48:29PM +0300, Jarkko Sakkinen wrote:
> > From: Jarkko Sakkinen <jarkko.sakkinen@opinsys.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@opinsys.com>
> 
> Reviewed-by: Jonathan McDowell <noodles@meta.com>

Thanks.

> 
> > ---
> > 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.
> 
> -- 
> Web [       Reality is for people with no grasp of fantasy.        ]
> site: https:// [                                          ]      Made by
> www.earth.li/~noodles/  [                      ]         HuggieTag 0.0.24

BR, Jarkko