linux-kernel - Re: [PATCH 2/4] fsi: occ: Log error for checksum failure

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Message-ID: <CACPK8XdbCpqqotgKtX+8_T8rBwrkLQiQuJSxPiDg7jwh8nF2CQ@mail.gmail.com>
Date:   Tue, 6 Apr 2021 07:21:15 +0000
From:   Joel Stanley <joel@....id.au>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-hwmon@...r.kernel.org, linux-fsi@...ts.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jeremy Kerr <jk@...abs.org>,
        Alistair Popple <alistair@...ple.id.au>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH 2/4] fsi: occ: Log error for checksum failure

On Tue, 9 Feb 2021 at 17:13, Eddie James <eajames@...ux.ibm.com> wrote:
>
> Log an error if the response checksum doesn't match the
> calculated checksum.

Reviewed-by: Joel Stanley <joel@....id.au>

>
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> ---
>  drivers/fsi/fsi-occ.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/fsi/fsi-occ.c b/drivers/fsi/fsi-occ.c
> index cb05b6dacc9d..524460995465 100644
> --- a/drivers/fsi/fsi-occ.c
> +++ b/drivers/fsi/fsi-occ.c
> @@ -223,7 +223,8 @@ static const struct file_operations occ_fops = {
>         .release = occ_release,
>  };
>
> -static int occ_verify_checksum(struct occ_response *resp, u16 data_length)
> +static int occ_verify_checksum(struct occ *occ, struct occ_response *resp,
> +                              u16 data_length)
>  {
>         /* Fetch the two bytes after the data for the checksum. */
>         u16 checksum_resp = get_unaligned_be16(&resp->data[data_length]);
> @@ -238,8 +239,11 @@ static int occ_verify_checksum(struct occ_response *resp, u16 data_length)
>         for (i = 0; i < data_length; ++i)
>                 checksum += resp->data[i];
>
> -       if (checksum != checksum_resp)
> +       if (checksum != checksum_resp) {
> +               dev_err(occ->dev, "Bad checksum: %04x!=%04x\n", checksum,
> +                       checksum_resp);

Just confirming that this is unexpected, we won't see this eg. if the
system is booting or when the BMC is reset while the host is running?

>                 return -EBADMSG;
> +       }
>
>         return 0;
>  }
> @@ -533,7 +537,7 @@ int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
>         }
>
>         *resp_len = resp_data_length + 7;
> -       rc = occ_verify_checksum(resp, resp_data_length);
> +       rc = occ_verify_checksum(occ, resp, resp_data_length);
>
>   done:
>         mutex_unlock(&occ->occ_lock);
> --
> 2.27.0
>