linux-kernel - Re: [PATCH v3 1/4] tpm_tis: Explicitly check for error code

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Message-ID: <8877c0d2592b5f93f3b1e8ba6e6d4db7a04a094f.camel@kernel.org>
Date:   Mon, 10 Jul 2023 19:58:25 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Alexander Steffen <Alexander.Steffen@...ineon.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH v3 1/4] tpm_tis: Explicitly check for error code

On Tue, 2023-06-13 at 20:02 +0200, Alexander Steffen wrote:
> recv_data either returns the number of received bytes, or a negative value
> representing an error code. Adding the return value directly to the total
> number of received bytes therefore looks a little weird, since it might add
> a negative error code to a sum of bytes.
> 
> The following check for size < expected usually makes the function return
> ETIME in that case, so it does not cause too many problems in practice. But
> to make the code look cleaner and because the caller might still be
> interested in the original error code, explicitly check for the presence of
> an error code and pass that through.
> 
> Cc: stable@...r.kernel.org
> Fixes: cb5354253af2 ("[PATCH] tpm: spacing cleanups 2")
> Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 558144fa707a..aaaa136044ae 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -363,8 +363,13 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>  		goto out;
>  	}
>  
> -	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
> -			  expected - TPM_HEADER_SIZE);
> +	rc = recv_data(chip, &buf[TPM_HEADER_SIZE],
> +		       expected - TPM_HEADER_SIZE);
> +	if (rc < 0) {
> +		size = rc;
> +		goto out;
> +	}
> +	size += rc;
>  	if (size < expected) {
>  		dev_err(&chip->dev, "Unable to read remainder of result\n");
>  		size = -ETIME;

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

BR, Jarkko