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Subject[PATCH] tpm: ibmvtpm: Avoid -EINTR error when IMA talks to TPM
Date
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':

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.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Fixes: 18b3670d79ae9 ("tpm: ibmvtpm: Add support for TPM2")
Cc: Nayna Jain <nayna@linux.ibm.com>
Cc: George Wilson <gcwilson@linux.ibm.com>
---
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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