linux-kernel - Re: [PATCH] tpm: ibmvtpm: Avoid error message when process gets signal while waiting

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Date:   Tue, 13 Jul 2021 10:33:02 +0530
From:   Nageswara Sastry <rnsastry@...ux.ibm.com>
To:     Stefan Berger <stefanb@...ux.vnet.ibm.com>, peterhuewe@....de,
        jarkko@...nel.org
Cc:     jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Stefan Berger <stefanb@...ux.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        George Wilson <gcwilson@...ux.ibm.com>
Subject: Re: [PATCH] tpm: ibmvtpm: Avoid error message when process gets
 signal while waiting



On 12/07/21 9:55 pm, Stefan Berger wrote:
> From: Stefan Berger <stefanb@...ux.ibm.com>
> 
> When rngd is run as root then lots of these types of message will appear
> in the kernel log if the TPM has been configure to provide random bytes:
> 
> [ 7406.275163] tpm tpm0: tpm_transmit: tpm_recv: error -4
> 
> The issue is caused by the following call that is interrupted while
> waiting for the TPM's response.
> 
> sig = wait_event_interruptible(ibmvtpm->wq,
>                                 !ibmvtpm->tpm_processing_cmd);
> 
> The solution is to use wait_event() instead.
> 
> To recreat the issue start rngd like this:
> 
> sudo rngd -r /dev/hwrng -t
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1981473
> Fixes: 6674ff145eef ("tpm_ibmvtpm: properly handle interrupted packet receptions")
> Cc: Nayna Jain <nayna@...ux.ibm.com>
> Cc: George Wilson <gcwilson@...ux.ibm.com>
> Reported-by: Nageswara R Sastry <rnsastry@...ux.ibm.com>
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>

Tested-by: Nageswara R Sastry <rnsastry@...ux.ibm.com>

> ---
>   drivers/char/tpm/tpm_ibmvtpm.c | 13 ++++---------
>   1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
> index 903604769de9..99b0442a5fdf 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.c
> +++ b/drivers/char/tpm/tpm_ibmvtpm.c
> @@ -106,16 +106,13 @@ static int tpm_ibmvtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>   {
>   	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
>   	u16 len;
> -	int sig;
>   
>   	if (!ibmvtpm->rtce_buf) {
>   		dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
>   		return 0;
>   	}
>   
> -	sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
> -	if (sig)
> -		return -EINTR;
> +	wait_event(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
>   
>   	len = ibmvtpm->res_len;
>   
> @@ -206,7 +203,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
>   {
>   	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
>   	bool retry = true;
> -	int rc, sig;
> +	int rc;
>   
>   	if (!ibmvtpm->rtce_buf) {
>   		dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
> @@ -224,9 +221,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
>   		dev_info(ibmvtpm->dev,
>   		         "Need to wait for TPM to finish\n");
>   		/* wait for previous command to finish */
> -		sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
> -		if (sig)
> -			return -EINTR;
> +		wait_event(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
>   	}
>   
>   	spin_lock(&ibmvtpm->rtce_lock);
> @@ -551,7 +546,7 @@ static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
>   			/* len of the data in rtce buffer */
>   			ibmvtpm->res_len = be16_to_cpu(crq->len);
>   			ibmvtpm->tpm_processing_cmd = false;
> -			wake_up_interruptible(&ibmvtpm->wq);
> +			wake_up(&ibmvtpm->wq);
>   			return;
>   		default:
>   			return;
> 

-- 
Thanks and Regards
R.Nageswara Sastry