linux-kernel - Re: [PATCH v3 1/2] tpm: Fix error handling in async work

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Date:   Wed, 12 Jan 2022 20:35:15 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Tadeusz Struk <tstruk@...il.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, linux-integrity@...r.kernel.org,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] tpm: Fix error handling in async work

On Mon, Jan 10, 2022 at 09:52:27PM -0800, Tadeusz Struk wrote:
> When an invalid (non existing) handle is used in a TPM command,
> that uses the resource manager interface (/dev/tpmrm0) the resource
> manager tries to load it from its internal cache, but fails and
> the tpm_dev_transmit returns an -EINVAL error to the caller.
> The existing async handler doesn't handle these error cases
> currently and the condition in the poll handler never returns
> mask with EPOLLIN set.
> The result is that the poll call blocks and the application gets stuck
> until the user_read_timer wakes it up after 120 sec.
> Change the tpm_dev_async_work function to handle error conditions
> returned from tpm_dev_transmit they are also reflected in the poll mask
> and a correct error code could passed back to the caller.
> 
> Cc: Jarkko Sakkinen <jarkko@...nel.org>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: <linux-integrity@...r.kernel.org>
> Cc: <stable@...r.kernel.org>
> Cc: <linux-kernel@...r.kernel.org>
> Fixes: 9e1b74a63f77 ("tpm: add support for nonblocking operation")
> Signed-off-by: Tadeusz Struk <tstruk@...il.com>
> ---
> Changed in v2:
> - Updated commit message with better problem description
> - Fixed typeos.
> Changed in v3:
> - Added a comment to tpm_dev_async_work.
> - Updated commit message.
> ---
>  drivers/char/tpm/tpm-dev-common.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index c08cbb306636..50df8f09ff79 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -69,7 +69,13 @@ static void tpm_dev_async_work(struct work_struct *work)
>  	ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
>  			       sizeof(priv->data_buffer));
>  	tpm_put_ops(priv->chip);
> -	if (ret > 0) {
> +
> +	/*
> +	 * If ret is > 0 then tpm_dev_transmit returned the size of the
> +	 * response. If ret is < 0 then tpm_dev_transmit failed and
> +	 * returned a return code.
> +	 */
> +	if (ret != 0) {
>  		priv->response_length = ret;
>  		mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
>  	}
> -- 
> 2.30.2
> 

These look good to me! Thank you. I'm in process of compiling a test
kernel.

/Jarkko