[PATCH] i2c: add sanity check to i2c_put_adapter

[PATCH] i2c: add sanity check to i2c_put_adapter

[Sebastian Hesselbarth]

i2c_put_adapter dereferences i2c_adapter pointer passed without check
for NULL. This adds a check for non-NULL pointer to allow i2c_put_adapter
called with NULL and behave the same way i2c_release_client does already.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
---
 drivers/i2c/i2c-core.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index f32ca29..d075df6 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1825,7 +1825,8 @@ EXPORT_SYMBOL(i2c_get_adapter);
 
 void i2c_put_adapter(struct i2c_adapter *adap)
 {
-	module_put(adap->owner);
+	if (adap)
+		module_put(adap->owner);
 }
 EXPORT_SYMBOL(i2c_put_adapter);
 
-- 
1.7.10.4

Re: [PATCH] i2c: add sanity check to i2c_put_adapter

[Wolfram Sang]

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On Thu, Aug 01, 2013 at 02:10:46PM +0200, Sebastian Hesselbarth wrote:
> i2c_put_adapter dereferences i2c_adapter pointer passed without check
> for NULL. This adds a check for non-NULL pointer to allow i2c_put_adapter
> called with NULL and behave the same way i2c_release_client does already.

What about using WARN for the NULL case to point out the ref-counting
imbalance?

> 
> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
> Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> ---
>  drivers/i2c/i2c-core.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index f32ca29..d075df6 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -1825,7 +1825,8 @@ EXPORT_SYMBOL(i2c_get_adapter);
>  
>  void i2c_put_adapter(struct i2c_adapter *adap)
>  {
> -	module_put(adap->owner);
> +	if (adap)
> +		module_put(adap->owner);
>  }
>  EXPORT_SYMBOL(i2c_put_adapter);
>  
> -- 
> 1.7.10.4
> 

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Re: [PATCH] i2c: add sanity check to i2c_put_adapter

[Sebastian Hesselbarth]

On 08/05/13 11:00, Wolfram Sang wrote:
> On Thu, Aug 01, 2013 at 02:10:46PM +0200, Sebastian Hesselbarth wrote:
>> i2c_put_adapter dereferences i2c_adapter pointer passed without check
>> for NULL. This adds a check for non-NULL pointer to allow i2c_put_adapter
>> called with NULL and behave the same way i2c_release_client does already.
>
> What about using WARN for the NULL case to point out the ref-counting
> imbalance?

Wolfram,

I was just adding this to (a) make it consistent with i2c_release_client
and (b) it allows to simplify drivers where you need to release the
adapter during probe failures. But that patch is so small, feel free to
squash in anything you like.

For a more sophisticated (WARN_ON) approach, I suggest to also put one
into i2c_release_client then.

Sebastian

>>
>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> ---
>> Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
>> Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>> Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>> ---
>>   drivers/i2c/i2c-core.c |    3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
>> index f32ca29..d075df6 100644
>> --- a/drivers/i2c/i2c-core.c
>> +++ b/drivers/i2c/i2c-core.c
>> @@ -1825,7 +1825,8 @@ EXPORT_SYMBOL(i2c_get_adapter);
>>
>>   void i2c_put_adapter(struct i2c_adapter *adap)
>>   {
>> -	module_put(adap->owner);
>> +	if (adap)
>> +		module_put(adap->owner);
>>   }
>>   EXPORT_SYMBOL(i2c_put_adapter);
>>
>> --
>> 1.7.10.4
>>

Re: [PATCH] i2c: add sanity check to i2c_put_adapter

[Wolfram Sang]

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On Mon, Aug 05, 2013 at 11:31:42AM +0200, Sebastian Hesselbarth wrote:
> On 08/05/13 11:00, Wolfram Sang wrote:
> >On Thu, Aug 01, 2013 at 02:10:46PM +0200, Sebastian Hesselbarth wrote:
> >>i2c_put_adapter dereferences i2c_adapter pointer passed without check
> >>for NULL. This adds a check for non-NULL pointer to allow i2c_put_adapter
> >>called with NULL and behave the same way i2c_release_client does already.
> >
> >What about using WARN for the NULL case to point out the ref-counting
> >imbalance?
> 
> Wolfram,
> 
> I was just adding this to (a) make it consistent with i2c_release_client
> and (b) it allows to simplify drivers where you need to release the
> adapter during probe failures. But that patch is so small, feel free to
> squash in anything you like.

I am not forcing you to do this, I am calling for opinions here.


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Re: [PATCH] i2c: add sanity check to i2c_put_adapter

[Wolfram Sang]

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On Thu, Aug 01, 2013 at 02:10:46PM +0200, Sebastian Hesselbarth wrote:
> i2c_put_adapter dereferences i2c_adapter pointer passed without check
> for NULL. This adds a check for non-NULL pointer to allow i2c_put_adapter
> called with NULL and behave the same way i2c_release_client does already.
> 
> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

Applied to for-next, thanks! Please describe the use case next time in
the patch description. The current text describes more what is changed
not why. You did that later ("easier probing").


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