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Message-ID: <YCZE8nf9ylXJTo4k@kernel.org>
Date: Fri, 12 Feb 2021 11:05:54 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Stefan Berger <stefanb@...ux.ibm.com>
Cc: linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
peterhuewe@....de, Nayna Jain <nayna@...ux.ibm.com>,
George Wilson <gcwilson@...ux.ibm.com>
Subject: Re: [PATCH] tpm: ibmvtpm: Avoid -EINTR error when IMA talks to TPM
On Tue, Feb 09, 2021 at 05:13:39PM -0500, Stefan Berger wrote:
> When IMA is taking measurements during compilation for example and a
> user presses ctrl-c to abort the compilation, lots of these types of
> messages will appear in the kernel log:
>
> [ 7406.275163] tpm tpm0: tpm_transmit: tpm_recv: error -4
> [ 7406.275242] ima: Error Communicating to TPM chip, result: -4
>
> The issue is caused by the fact that the IBM vTPM driver's recv()
> function is called immediately after send() without waiting for
> status on whether a response was received. It currently waits for
> the current command to finish using this call that ends up throwing
> these error messages because it is 'interruptible':
Why it is an issue?
> sig = wait_event_interruptible(ibmvtpm->wq,
> !ibmvtpm->tpm_processing_cmd);
>
> Instead, it should be using the polling loop in tpm_try_transmit()
> that uses a command's duration to poll until a result has been
> returned by the TPM, thus ending when the timeout has occurred but
> not responding to users' ctrl-c request anymore. To stay in this
> polling loop we now extend tpm_ibmvtpm_status() to return
> PM_STATUS_BUSY for as long as the vTPM is busy. Since we will need
> the timeouts in this loop now we get the TPM 1.2 and TPM 2 timeouts
> with tpm_get_timeouts().
>
> We change tpm_processing_cmd to tpm_status and set the TPM_STATUS_BUSY
> flag while the vTPM is busy processing a command.
Please, never use "we". The commit message should describe in
imperative form the action taken.
>
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
> Fixes: 18b3670d79ae9 ("tpm: ibmvtpm: Add support for TPM2")
> Cc: Nayna Jain <nayna@...ux.ibm.com>
> Cc: George Wilson <gcwilson@...ux.ibm.com>
Your SOB should be last.
> ---
> drivers/char/tpm/tpm_ibmvtpm.c | 31 ++++++++++++++++++-------------
> drivers/char/tpm/tpm_ibmvtpm.h | 3 ++-
> 2 files changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
> index 994385bf37c0..6290bd8889e4 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.c
> +++ b/drivers/char/tpm/tpm_ibmvtpm.c
> @@ -106,17 +106,12 @@ 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;
> -
> len = ibmvtpm->res_len;
>
> if (count < len) {
> @@ -220,11 +215,12 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
> return -EIO;
> }
>
> - if (ibmvtpm->tpm_processing_cmd) {
> + if ((ibmvtpm->tpm_status & TPM_STATUS_BUSY)) {
> 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);
> + sig = wait_event_interruptible(ibmvtpm->wq,
> + (ibmvtpm->tpm_status & TPM_STATUS_BUSY) == 0);
> if (sig)
> return -EINTR;
> }
> @@ -237,7 +233,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
> * set the processing flag before the Hcall, since we may get the
> * result (interrupt) before even being able to check rc.
> */
> - ibmvtpm->tpm_processing_cmd = true;
> + ibmvtpm->tpm_status |= TPM_STATUS_BUSY;
>
> again:
> rc = ibmvtpm_send_crq(ibmvtpm->vdev,
> @@ -255,7 +251,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
> goto again;
> }
> dev_err(ibmvtpm->dev, "tpm_ibmvtpm_send failed rc=%d\n", rc);
> - ibmvtpm->tpm_processing_cmd = false;
> + ibmvtpm->tpm_status &= ~TPM_STATUS_BUSY;
> }
>
> spin_unlock(&ibmvtpm->rtce_lock);
> @@ -269,7 +265,9 @@ static void tpm_ibmvtpm_cancel(struct tpm_chip *chip)
>
> static u8 tpm_ibmvtpm_status(struct tpm_chip *chip)
> {
> - return 0;
> + struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
> +
> + return ibmvtpm->tpm_status;
> }
>
> /**
> @@ -459,7 +457,7 @@ static const struct tpm_class_ops tpm_ibmvtpm = {
> .send = tpm_ibmvtpm_send,
> .cancel = tpm_ibmvtpm_cancel,
> .status = tpm_ibmvtpm_status,
> - .req_complete_mask = 0,
> + .req_complete_mask = TPM_STATUS_BUSY,
> .req_complete_val = 0,
> .req_canceled = tpm_ibmvtpm_req_canceled,
> };
> @@ -552,7 +550,7 @@ static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
> case VTPM_TPM_COMMAND_RES:
> /* len of the data in rtce buffer */
> ibmvtpm->res_len = be16_to_cpu(crq->len);
> - ibmvtpm->tpm_processing_cmd = false;
> + ibmvtpm->tpm_status &= ~TPM_STATUS_BUSY;
> wake_up_interruptible(&ibmvtpm->wq);
> return;
> default:
> @@ -690,8 +688,15 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
> goto init_irq_cleanup;
> }
>
> - if (!strcmp(id->compat, "IBM,vtpm20")) {
> +
> + if (!strcmp(id->compat, "IBM,vtpm20"))
> chip->flags |= TPM_CHIP_FLAG_TPM2;
> +
> + rc = tpm_get_timeouts(chip);
> + if (rc)
> + goto init_irq_cleanup;
> +
> + if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> rc = tpm2_get_cc_attrs_tbl(chip);
> if (rc)
> goto init_irq_cleanup;
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.h b/drivers/char/tpm/tpm_ibmvtpm.h
> index b92aa7d3e93e..252f1cccdfc5 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.h
> +++ b/drivers/char/tpm/tpm_ibmvtpm.h
> @@ -41,7 +41,8 @@ struct ibmvtpm_dev {
> wait_queue_head_t wq;
> u16 res_len;
> u32 vtpm_version;
> - bool tpm_processing_cmd;
> + u8 tpm_status;
> +#define TPM_STATUS_BUSY (1 << 0) /* vtpm is processing a command */
> };
>
> #define CRQ_RES_BUF_SIZE PAGE_SIZE
> --
> 2.29.2
>
>
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