Re: [PATCH v6 6/8] tpm: TPM2B formatted buffers

[Stefan Berger]

On 11/23/23 21:02, Jarkko Sakkinen wrote:
> Declare tpm_buf_init_sized() and tpm_buf_reset_sized() for creating TPM2B
> formatted buffers. These buffers are also known as sized buffers in the
> specifications and literature.
>
> Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>

Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>

> ---
> v2: [2021-11-21] Refine the API according to the comments for
>      https://lore.kernel.org/linux-integrity/20231024011531.442587-5-jarkko@xxxxxxxxxx/
> ---
>   drivers/char/tpm/tpm-buf.c | 38 +++++++++++++++++++++++++++++++++++---
>   include/linux/tpm.h        |  4 ++++
>   2 files changed, 39 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index 3f39893f3bb1..099b4a56c5d5 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -47,6 +47,36 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>   }
>   EXPORT_SYMBOL_GPL(tpm_buf_reset);
>   
> +/**
> + * tpm_buf_init_sized() - Allocate and initialize a sized (TPM2B) buffer
> + * @buf:	A @tpm_buf
> + *
> + * Return: 0 or -ENOMEM
> + */
> +int tpm_buf_init_sized(struct tpm_buf *buf)
> +{
> +	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
> +	if (!buf->data)
> +		return -ENOMEM;
> +
> +	tpm_buf_reset_sized(buf);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
> +
> +/**
> + * tpm_buf_reset_sized() - Initialize a sized buffer
> + * @buf:	A &tpm_buf
> + */
> +void tpm_buf_reset_sized(struct tpm_buf *buf)
> +{
> +	buf->flags = TPM_BUF_TPM2B;
> +	buf->length = 2;
> +	buf->data[0] = 0;
> +	buf->data[1] = 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
> +
>   void tpm_buf_destroy(struct tpm_buf *buf)
>   {
>   	free_page((unsigned long)buf->data);
> @@ -72,8 +102,6 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
>    */
>   void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
>   {
> -	struct tpm_header *head = (struct tpm_header *)buf->data;
> -
>   	/* Return silently if overflow has already happened. */
>   	if (buf->flags & TPM_BUF_OVERFLOW)
>   		return;
> @@ -86,7 +114,11 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
>   
>   	memcpy(&buf->data[buf->length], new_data, new_length);
>   	buf->length += new_length;
> -	head->length = cpu_to_be32(buf->length);
> +
> +	if (buf->flags & TPM_BUF_TPM2B)
> +		((__be16 *)buf->data)[0] = cpu_to_be16(buf->length - 2);
> +	else
> +		((struct tpm_header *)buf->data)->length = cpu_to_be32(buf->length);
>   }
>   EXPORT_SYMBOL_GPL(tpm_buf_append);
>   
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 1d7b39b5c383..715db4a91c1f 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -300,6 +300,8 @@ struct tpm_header {
>   enum tpm_buf_flags {
>   	/* the capacity exceeded: */
>   	TPM_BUF_OVERFLOW	= BIT(0),
> +	/* TPM2B format: */
> +	TPM_BUF_TPM2B		= BIT(1),
>   };
>   
>   /*
> @@ -328,6 +330,8 @@ struct tpm2_hash {
>   
>   int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
>   void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
> +int tpm_buf_init_sized(struct tpm_buf *buf);
> +void tpm_buf_reset_sized(struct tpm_buf *buf);
>   void tpm_buf_destroy(struct tpm_buf *buf);
>   u32 tpm_buf_length(struct tpm_buf *buf);
>   void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);