Re: [PATCH 1/4] tpm: fix access attempt to an already unmapped I/O memory region

Jason Gunthorpe
2017-12-20T18:08:57Z

On Wed, Dec 20, 2017 at 12:35:35PM +0100, Javier Martinez Canillas wrote:
> The driver maps the I/O memory address to control the LPC bus CLKRUN_EN,
> but on the error path the memory is accessed by the .clk_enable handler
> after this was already unmapped. So only unmap the I/O memory region if
> it will not be used anymore.
>
> Also, the correct thing to do is to cleanup the resources in the inverse
> order that were acquired to prevent issues like these.
>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>
> drivers/char/tpm/tpm_tis_core.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index c2227983ed88..3455abbb2035 100644
> +++ b/drivers/char/tpm/tpm_tis_core.c

Yoiks. This patch is helping but the more I look at this the wronger
everything looks..

1) tpm_chip_unregister makes chip->ops == NULL, so this sequence:

static int tpm_tis_plat_remove(struct platform_device *pdev)
tpm_chip_unregister(chip);
tpm_tis_remove(chip);
void tpm_tis_remove(struct tpm_chip *chip)
if (chip->ops->clk_enable != NULL)

Will oops

2) tpm_chip_register can also NULL ops in error cases, so this
sequence can oops:

rc = tpm_chip_register(chip);
if (rc && is_bsw())
iounmap(priv->ilb_base_addr);

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

3) iounmap should not be split between tpm_tis and tpm_tis_core
Put it at the end of tpm_tis_remove.

4) This sequence:

+ return tpm_chip_register(chip);
+out_err:
+ tpm_tis_remove(chip);
+ return rc;

Doesn't look right. If tpm_chip_register fails then
tpm_tis_remove will never be called. This was sort of OK when
tpm_tis_remove didn't manage any resources, but now that it does
the above needs fixing too.

The below draft fixes everything except #1. That needs a more thoughtful
idea..

Jason

diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
index d29add49b03388..09f18e2e644774 100644
--- a/drivers/char/tpm/tpm_tis.c
+++ b/drivers/char/tpm/tpm_tis.c
@@ -275,9 +275,6 @@ static void tpm_tis_pnp_remove(struct pnp_dev *dev)

tpm_chip_unregister(chip);
tpm_tis_remove(chip);
- if (is_bsw())
- iounmap(priv->ilb_base_addr);
-
}

static struct pnp_driver tis_pnp_driver = {
@@ -328,10 +325,6 @@ static int tpm_tis_plat_remove(struct platform_device *pdev)

tpm_chip_unregister(chip);
tpm_tis_remove(chip);
-
- if (is_bsw())
- iounmap(priv->ilb_base_addr);
-
return 0;
}

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index c2227983ed88d4..ffda1694a6aba3 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -727,6 +727,9 @@ void tpm_tis_remove(struct tpm_chip *chip)

if (chip->ops->clk_enable != NULL)
chip->ops->clk_enable(chip, false);
+
+ if (priv->ilb_base_addr)
+ iounmap(priv->ilb_base_addr);
}
EXPORT_SYMBOL_GPL(tpm_tis_remove);

@@ -921,22 +924,15 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
}
}

- rc = tpm_chip_register(chip);
- if (rc && is_bsw())
- iounmap(priv->ilb_base_addr);
-
if (chip->ops->clk_enable != NULL)
chip->ops->clk_enable(chip, false);

- return rc;
+ rc = tpm_chip_register(chip);
+ if (rc):
+ goto out_err;
+ return 0;
out_err:
tpm_tis_remove(chip);
- if (is_bsw())
- iounmap(priv->ilb_base_addr);
-
- if (chip->ops->clk_enable != NULL)
- chip->ops->clk_enable(chip, false);
-
return rc;
}
EXPORT_SYMBOL_GPL(tpm_tis_core_init);