[PATCH] tpm: return -ENODEV if np is not set

[PATCH] tpm: return -ENODEV if np is not set

[Colin King]

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

device_node np contains a garbage value from the stack and it
is only set if chip->dev.parent->of_node is not null.  Thus the
check for a null np won't spot a garbage value of np from the
stack if chip->dev.parent->of_node is null and if np contains
an garbage non-null value.

I believe the correct fix is to return -ENODEV if and only if
chip->dev.parent->of_node is null.

Found with static analysis by CoverityScan, CID 1377755

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/char/tpm/tpm_of.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_of.c b/drivers/char/tpm/tpm_of.c
index 3af829f..1426590 100644
--- a/drivers/char/tpm/tpm_of.c
+++ b/drivers/char/tpm/tpm_of.c
@@ -31,7 +31,7 @@ int read_log_of(struct tpm_chip *chip)
 	log = &chip->log;
 	if (chip->dev.parent->of_node)
 		np = chip->dev.parent->of_node;
-	if (!np)
+	else
 		return -ENODEV;
 
 	sizep = of_get_property(np, "linux,sml-size", NULL);
-- 
2.10.2

Re: [PATCH] tpm: return -ENODEV if np is not set

[Jarkko Sakkinen]

On Tue, Nov 15, 2016 at 01:27:22PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
> 
> device_node np contains a garbage value from the stack and it
> is only set if chip->dev.parent->of_node is not null.  Thus the
> check for a null np won't spot a garbage value of np from the
> stack if chip->dev.parent->of_node is null and if np contains
> an garbage non-null value.
> 
> I believe the correct fix is to return -ENODEV if and only if
> chip->dev.parent->of_node is null.
> 
> Found with static analysis by CoverityScan, CID 1377755
> 
> Signed-off-by: Colin Ian King <colin.king-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

/Jarkko

> ---
>  drivers/char/tpm/tpm_of.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/tpm_of.c b/drivers/char/tpm/tpm_of.c
> index 3af829f..1426590 100644
> --- a/drivers/char/tpm/tpm_of.c
> +++ b/drivers/char/tpm/tpm_of.c
> @@ -31,7 +31,7 @@ int read_log_of(struct tpm_chip *chip)
>  	log = &chip->log;
>  	if (chip->dev.parent->of_node)
>  		np = chip->dev.parent->of_node;
> -	if (!np)
> +	else
>  		return -ENODEV;
>  
>  	sizep = of_get_property(np, "linux,sml-size", NULL);
> -- 
> 2.10.2
> 

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