[PATCH] tpm: st33zp24: check if chip is null before dereferencing

[PATCH] tpm: st33zp24: check if chip is null before dereferencing

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

Currently chip is being dereferenced by the call to dev_get_drvdata
before it is being null checked, hence we have a potential null
pointer dereference bug. Fix this by only dereferencing it after the
null check.

Detected by CoverityScan, CID#1357806 ("Dereference before null check")

Fixes: 9e0d39d8a6a0 ("tpm: Remove useless priv field in struct tpm_vendor_specific")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/char/tpm/st33zp24/st33zp24.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/st33zp24/st33zp24.c b/drivers/char/tpm/st33zp24/st33zp24.c
index f95b9c75175b..476865d66a0e 100644
--- a/drivers/char/tpm/st33zp24/st33zp24.c
+++ b/drivers/char/tpm/st33zp24/st33zp24.c
@@ -367,7 +367,7 @@ static irqreturn_t tpm_ioserirq_handler(int irq, void *dev_id)
 static int st33zp24_send(struct tpm_chip *chip, unsigned char *buf,
 			 size_t len)
 {
-	struct st33zp24_dev *tpm_dev = dev_get_drvdata(&chip->dev);
+	struct st33zp24_dev *tpm_dev;
 	u32 status, i, size, ordinal;
 	int burstcnt = 0;
 	int ret;
@@ -378,6 +378,7 @@ static int st33zp24_send(struct tpm_chip *chip, unsigned char *buf,
 	if (len < TPM_HEADER_SIZE)
 		return -EBUSY;
 
+	tpm_dev = dev_get_drvdata(&chip->dev);
 	ret = request_locality(chip);
 	if (ret < 0)
 		return ret;
-- 
2.15.1

Re: [PATCH] tpm: st33zp24: check if chip is null before dereferencing

[Jason Gunthorpe]

On Fri, Apr 06, 2018 at 05:05:41PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently chip is being dereferenced by the call to dev_get_drvdata
> before it is being null checked, hence we have a potential null
> pointer dereference bug. Fix this by only dereferencing it after the
> null check.
> 
> Detected by CoverityScan, CID#1357806 ("Dereference before null check")
> 
> Fixes: 9e0d39d8a6a0 ("tpm: Remove useless priv field in struct tpm_vendor_specific")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>  drivers/char/tpm/st33zp24/st33zp24.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/st33zp24/st33zp24.c b/drivers/char/tpm/st33zp24/st33zp24.c
> index f95b9c75175b..476865d66a0e 100644
> +++ b/drivers/char/tpm/st33zp24/st33zp24.c
> @@ -367,7 +367,7 @@ static irqreturn_t tpm_ioserirq_handler(int irq, void *dev_id)
>  static int st33zp24_send(struct tpm_chip *chip, unsigned char *buf,
>  			 size_t len)
>  {
> -	struct st33zp24_dev *tpm_dev = dev_get_drvdata(&chip->dev);
> +	struct st33zp24_dev *tpm_dev;
>  	u32 status, i, size, ordinal;
>  	int burstcnt = 0;
>  	int ret;

Chip can't be NULL here, so I would prefer to see the NULL test
deleted.

Thanks,
Jason

Re: [PATCH] tpm: st33zp24: check if chip is null before dereferencing

[Sasha Levin]

Hi,

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag,
fixing commit: 9e0d39d8a6a0 tpm: Remove useless priv field in struct tpm_vendor_specific.

The bot has also determined it's probably a bug fixing patch. (score: 19.6716)

The bot has tested the following trees: v4.16.1, v4.15.16, v4.14.33, v4.9.93.

v4.16.1: Build OK!
v4.15.16: Build OK!
v4.14.33: Build OK!
v4.9.93: Build OK!

--
Thanks,
Sasha