RE: [PATCH] tpm: Fix the driver cleanup code

From: Shaikh, Azhar
Date: Thu Dec 21 2017 - 16:54:46 EST

>-----Original Message-----
>From: linux-integrity-owner@xxxxxxxxxxxxxxx [mailto:linux-integrity-
>owner@xxxxxxxxxxxxxxx] On Behalf Of Jason Gunthorpe
>Sent: Thursday, December 21, 2017 12:39 PM
>To: Shaikh, Azhar <azhar.shaikh@xxxxxxxxx>
>Cc: jarkko.sakkinen@xxxxxxxxxxxxxxx; javierm@xxxxxxxxxx;
>peterhuewe@xxxxxx; linux-security-module@xxxxxxxxxxxxxxx; linux-
>integrity@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; tpmdd-
>Subject: Re: [PATCH] tpm: Fix the driver cleanup code
>On Thu, Dec 21, 2017 at 08:31:14PM +0000, Shaikh, Azhar wrote:
>> Yes I thought about it too. But if some other chip->ops function in
>> future, which *might* be in this same case, hence for that introduced
>> this flag.
>It can't be - the ops struct is constant, can't be modified, and tpm_tis_core
>controls what is set. If someone future person meddles in this then they can
>fix here to.
Yes, I checked this part. What I was referring to is any other callback function similar to clk_enable if gets added in future and then needs to
Access ops even after it is set to NULL...

>Recommend a short comment in the ops clk_enale initializer and call direct?

But yes I get your point now.

So do you mean something like this?

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index d9099281fc2e..1187e72483f2 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -716,8 +716,7 @@ void tpm_tis_remove(struct tpm_chip *chip)
u32 interrupt;
int rc;

- if (chip->ops->clk_enable != NULL)
- chip->ops->clk_enable(chip, true);
+ tpm_tis_clkrun_enable(chip, true);

rc = tpm_tis_read32(priv, reg, &interrupt);
if (rc < 0)
@@ -725,14 +724,8 @@ void tpm_tis_remove(struct tpm_chip *chip)

tpm_tis_write32(priv, reg, ~TPM_GLOBAL_INT_ENABLE & interrupt);

- if (chip->ops->clk_enable != NULL)
- chip->ops->clk_enable(chip, false);
+ tpm_tis_clkrun_enable(chip, false);

- if (chip->flags & TPM_CHIP_FLAG_DO_NOT_CLEAR_OPS) {
- down_write(&chip->ops_sem);
- chip->ops = NULL;
- up_write(&chip->ops_sem);
- }
if (priv->ilb_base_addr)


Azhar Shaikh