linux-kernel - Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

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Date:   Thu, 26 Oct 2023 10:10:26 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        William Roberts <bill.c.roberts@...il.com>,
        Stefan Berger <stefanb@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Peter Huewe <peterhuewe@....de>,
        Mario Limonciello <mario.limonciello@....com>,
        Julien Gomes <julien@...sta.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to
 real functions

On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
> 
> On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
> >
> 
> Thanks I'll add it to the next round.
> 
> For the tpm_buf_read(), I was thinking along the lines of:
> 
> /**
>  * tpm_buf_read() - Read from a TPM buffer
>  * @buf:	&tpm_buf instance
>  * @pos:	position within the buffer
>  * @count:	the number of bytes to read
>  * @output:	the output buffer
>  *
>  * Read bytes from a TPM buffer, and update the position. Returns false when the
>  * amount of bytes requested would overflow the buffer, which is expected to
>  * only happen in the case of hardware failure.
>  */
> static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos, size_t count, void *output)
> {
> 	off_t next = *pos + count;
> 
> 	if (next >= buf->length) {
> 		pr_warn("%s: %lu >= %lu\n", __func__, next, *offset);
> 		return false;
> 	}
> 
> 	memcpy(output, &buf->data[*pos], count);
> 	*offset = next;
> 	return true;
> }
> 
> BR, Jarkko
> 

Then the callers will check, and return -EIO?