[tpmdd-devel,1/2] tpm_tis_core: add optional max xfer size check
diff mbox

Message ID 1468546745-14646-2-git-send-email-apronin@chromium.org
State New
Headers show

Commit Message

apronin@chromium.org July 15, 2016, 1:39 a.m. UTC
If tpm reports a bigger burstcnt than allowed by the physical protocol,
re-query the burstcnt and correct, if needed, if still too large.

In practice, seen in case of xfer issues (e.g. in spi interface case,
lost header causing flow control issues and wrong values returned on read
from TPM_STS). Without catching, causes the physical layer to reject xfer,
while is easily preventable by re-querying TPM_STS.

Signed-off-by: Andrey Pronin <apronin@chromium.org>
---
 drivers/char/tpm/tpm_tis_core.c | 17 +++++++++++++++--
 drivers/char/tpm/tpm_tis_core.h | 13 +++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

Comments

Jason Gunthorpe July 15, 2016, 3:13 a.m. UTC | #1
On Thu, Jul 14, 2016 at 06:39:04PM -0700, Andrey Pronin wrote:

> +static inline u16 tpm_tis_max_xfer_size(struct tpm_tis_data *data)
> +{
> +	return data->phy_ops->max_xfer_size;
> +}
> +
> +static inline bool tpm_tis_burstcnt_is_valid(struct tpm_tis_data *data,
> +					     u16 burstcnt)
> +{
> +	return (tpm_tis_max_xfer_size(data) == 0)
> +		|| (burstcnt <= tpm_tis_max_xfer_size(data));
> +}

We don't need these accessors, just open code it in the one call
site. That is more clear as the ==0 case is important to understand
that the flow is correct.

BTW, I dodn't think || as the start of a line was cannonical kernel
style.. Did checkpatch accept that?

Jason

------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are 
consuming the most bandwidth. Provides multi-vendor support for NetFlow, 
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports.http://sdm.link/zohodev2dev
apronin@chromium.org July 15, 2016, 3:25 a.m. UTC | #2
On Thu, Jul 14, 2016 at 09:13:51PM -0600, Jason Gunthorpe wrote:
> On Thu, Jul 14, 2016 at 06:39:04PM -0700, Andrey Pronin wrote:
> 
> > +static inline u16 tpm_tis_max_xfer_size(struct tpm_tis_data *data)
> > +{
> > +	return data->phy_ops->max_xfer_size;
> > +}
> > +
> > +static inline bool tpm_tis_burstcnt_is_valid(struct tpm_tis_data *data,
> > +					     u16 burstcnt)
> > +{
> > +	return (tpm_tis_max_xfer_size(data) == 0)
> > +		|| (burstcnt <= tpm_tis_max_xfer_size(data));
> > +}
> 
> We don't need these accessors, just open code it in the one call
> site. That is more clear as the ==0 case is important to understand
> that the flow is correct.
> 
> BTW, I dodn't think || as the start of a line was cannonical kernel
> style.. Did checkpatch accept that?
> 
> Jason

You mean completely open code it inside get_burstcount()? Will do.
checkpatch.pl had no problems with it, but I can move it to the end
of the line, if it feels better.

Andrey

------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are 
consuming the most bandwidth. Provides multi-vendor support for NetFlow, 
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports.http://sdm.link/zohodev2dev
Guenter Roeck July 15, 2016, 3:48 a.m. UTC | #3
On Thu, Jul 14, 2016 at 8:25 PM, Andrey Pronin <apronin@chromium.org> wrote:
> On Thu, Jul 14, 2016 at 09:13:51PM -0600, Jason Gunthorpe wrote:
>> On Thu, Jul 14, 2016 at 06:39:04PM -0700, Andrey Pronin wrote:
>>
>> > +static inline u16 tpm_tis_max_xfer_size(struct tpm_tis_data *data)
>> > +{
>> > +   return data->phy_ops->max_xfer_size;
>> > +}
>> > +
>> > +static inline bool tpm_tis_burstcnt_is_valid(struct tpm_tis_data *data,
>> > +                                        u16 burstcnt)
>> > +{
>> > +   return (tpm_tis_max_xfer_size(data) == 0)
>> > +           || (burstcnt <= tpm_tis_max_xfer_size(data));
>> > +}
>>
>> We don't need these accessors, just open code it in the one call
>> site. That is more clear as the ==0 case is important to understand
>> that the flow is correct.
>>
>> BTW, I dodn't think || as the start of a line was cannonical kernel
>> style.. Did checkpatch accept that?
>>
>> Jason
>
> You mean completely open code it inside get_burstcount()? Will do.
> checkpatch.pl had no problems with it, but I can move it to the end
> of the line, if it feels better.
>

I would suggest to use checkpatch --strict; it will tell you. It will
also ask you to align continuation lines with '(' on the previous
line. On that, I would suggest to follow the style used in the file(s)
you are working on (or follow guidance from the maintainer).

Thanks,
Guenter

------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are 
consuming the most bandwidth. Provides multi-vendor support for NetFlow, 
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports.http://sdm.link/zohodev2dev
Jarkko Sakkinen July 18, 2016, 6:53 p.m. UTC | #4
On Thu, Jul 14, 2016 at 09:13:51PM -0600, Jason Gunthorpe wrote:
> On Thu, Jul 14, 2016 at 06:39:04PM -0700, Andrey Pronin wrote:
> 
> > +static inline u16 tpm_tis_max_xfer_size(struct tpm_tis_data *data)
> > +{
> > +	return data->phy_ops->max_xfer_size;
> > +}
> > +
> > +static inline bool tpm_tis_burstcnt_is_valid(struct tpm_tis_data *data,
> > +					     u16 burstcnt)
> > +{
> > +	return (tpm_tis_max_xfer_size(data) == 0)
> > +		|| (burstcnt <= tpm_tis_max_xfer_size(data));
> > +}
> 
> We don't need these accessors, just open code it in the one call
> site. That is more clear as the ==0 case is important to understand
> that the flow is correct.

+1 They add only indirection here with no value.


> BTW, I dodn't think || as the start of a line was cannonical kernel
> style.. Did checkpatch accept that?
> 
> Jason

/Jarkko

------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are 
consuming the most bandwidth. Provides multi-vendor support for NetFlow, 
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports.http://sdm.link/zohodev2dev

Patch
diff mbox

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 8110b52..f5d456c 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -158,6 +158,7 @@  static int get_burstcount(struct tpm_chip *chip)
 	unsigned long stop;
 	int burstcnt, rc;
 	u32 value;
+	bool retry_burstcnt = false;
 
 	/* wait for burstcount */
 	/* which timeout value, spec has 2 answers (c & d) */
@@ -168,8 +169,20 @@  static int get_burstcount(struct tpm_chip *chip)
 			return rc;
 
 		burstcnt = (value >> 8) & 0xFFFF;
-		if (burstcnt)
-			return burstcnt;
+		if (burstcnt) {
+			/* If burstcnt is larger than max allowed xfer
+			 * size, retry once - may be a glitch. Return
+			 * max_xfer_size on the 2nd try to avoid being
+			 * stuck forever.
+			 */
+			if (tpm_tis_burstcnt_is_valid(priv, burstcnt))
+				return burstcnt;
+			if (retry_burstcnt)
+				return tpm_tis_max_xfer_size(priv);
+			dev_warn(&chip->dev, "Bad burstcnt read: %d\n",
+				 burstcnt);
+			retry_burstcnt = true;
+		}
 		msleep(TPM_TIMEOUT);
 	} while (time_before(jiffies, stop));
 	return -EBUSY;
diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index 9191aab..713aa5a 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -102,6 +102,7 @@  struct tpm_tis_phy_ops {
 	int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
 	int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
 	int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
+	u16 max_xfer_size;
 };
 
 static inline int tpm_tis_read_bytes(struct tpm_tis_data *data, u32 addr,
@@ -144,6 +145,18 @@  static inline int tpm_tis_write32(struct tpm_tis_data *data, u32 addr,
 	return data->phy_ops->write32(data, addr, value);
 }
 
+static inline u16 tpm_tis_max_xfer_size(struct tpm_tis_data *data)
+{
+	return data->phy_ops->max_xfer_size;
+}
+
+static inline bool tpm_tis_burstcnt_is_valid(struct tpm_tis_data *data,
+					     u16 burstcnt)
+{
+	return (tpm_tis_max_xfer_size(data) == 0)
+		|| (burstcnt <= tpm_tis_max_xfer_size(data));
+}
+
 void tpm_tis_remove(struct tpm_chip *chip);
 int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
 		      const struct tpm_tis_phy_ops *phy_ops,