Re: [PATCH v2 1/2] tpm: Fix error handling in async work

From: Jarkko Sakkinen <jarkko@kernel.org>
To: Tadeusz Struk <tstruk@gmail.com>, jarkko@kernel.org
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
	linux-integrity@vger.kernel.org, stable@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] tpm: Fix error handling in async work
Date: Wed, 05 Jan 2022 22:05:18 +0200	[thread overview]
Message-ID: <883e4ac1a10dc192824dff3eb6489d027417d1d4.camel@kernel.org> (raw)
In-Reply-To: <20211229050655.2030-1-tstruk@gmail.com>

On Tue, 2021-12-28 at 21:06 -0800, Tadeusz Struk wrote:
> When an invalid (non existing) handle is used in a tpm command,
                                                     ~~~
                                                     TPM

> that uses the resource manager interface (/dev/tpmrm0) the resource
> manager tries to load it from its internal cache, but fails and
> returns an -EINVAL error to the caller. The 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.
> Make sure that error conditions also contribute to the poll mask
> so that a correct error code could passed back to the caller.

I'm not sure what "making sure" means.

> 
> Cc: Jarkko Sakkinen <jarkko@kernel.org>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: <linux-integrity@vger.kernel.org>
> Cc: <stable@vger.kernel.org>
> Cc: <linux-kernel@vger.kernel.org>
> Fixes: 9e1b74a63f77 ("tpm: add support for nonblocking operation")
> Signed-off-by: Tadeusz Struk <tstruk@gmail.com>
> ---
> Changes in v2:
> - Updated commit message with better problem description.
> - Fixed typeos.
> ---
>  drivers/char/tpm/tpm-dev-common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/tpm-dev-common.c
> b/drivers/char/tpm/tpm-dev-common.c
> index c08cbb306636..fe2679f84cb6 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -69,7 +69,7 @@ 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 != 0) {

What if ret < 0?

You should explain this change in the commit message. Also, consider
adding an inline comment.

>                 priv->response_length = ret;
>                 mod_timer(&priv->user_read_timer, jiffies + (120 *
> HZ));
>         }

BR,
Jarkko