[PATCH] function mana_hwc_create_wq leaks memory

[PATCH] function mana_hwc_create_wq leaks memory

[Dhiraj Shah]

memory space allocated for the queue in function
mana_gd_create_hwc_queue is not freed during error condition.

Signed-off-by: Dhiraj Shah <find.dhiraj@gmail.com>
---
 drivers/net/ethernet/microsoft/mana/hw_channel.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c
index 1a923fd99990..4aa4bda518fb 100644
--- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
+++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
@@ -501,8 +501,10 @@ static int mana_hwc_create_wq(struct hw_channel_context *hwc,
 	*hwc_wq_ptr = hwc_wq;
 	return 0;
 out:
-	if (err)
+	if (err) {
+		kfree(queue);
 		mana_hwc_destroy_wq(hwc, hwc_wq);
+	}
 	return err;
 }
 
-- 
2.30.1 (Apple Git-130)

RE: [PATCH] function mana_hwc_create_wq leaks memory

[Dexuan Cui]

> From: Dhiraj Shah <find.dhiraj@gmail.com>
> Sent: Thursday, June 10, 2021 8:29 AM
>  ...
> memory space allocated for the queue in function
> mana_gd_create_hwc_queue is not freed during error condition.
> 
> Signed-off-by: Dhiraj Shah <find.dhiraj@gmail.com>
> ---
>  drivers/net/ethernet/microsoft/mana/hw_channel.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> index 1a923fd99990..4aa4bda518fb 100644
> --- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> +++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> @@ -501,8 +501,10 @@ static int mana_hwc_create_wq(struct
> hw_channel_context *hwc,
>  	*hwc_wq_ptr = hwc_wq;
>  	return 0;
>  out:
> -	if (err)
> +	if (err) {

Here the 'err' must be non-zero. Can you please remove this 'if'?

> +		kfree(queue);
>  		mana_hwc_destroy_wq(hwc, hwc_wq);
> +	}
>  	return err;
>  }

Reviewed-by: Dexuan Cui <decui@microsoft.com>

RE: [PATCH] function mana_hwc_create_wq leaks memory

[Dexuan Cui]

> From: Dexuan Cui <decui@microsoft.com>
> Sent: Thursday, June 10, 2021 10:18 AM
> ...
> > diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> > b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> > index 1a923fd99990..4aa4bda518fb 100644
> > --- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> > +++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> > @@ -501,8 +501,10 @@ static int mana_hwc_create_wq(struct
> > hw_channel_context *hwc,
> >  	*hwc_wq_ptr = hwc_wq;
> >  	return 0;
> >  out:
> > -	if (err)
> > +	if (err) {
> 
> Here the 'err' must be non-zero. Can you please remove this 'if'?
> 
> > +		kfree(queue);
> >  		mana_hwc_destroy_wq(hwc, hwc_wq);
> > +	}
> >  	return err;
> >  }
> 
> Reviewed-by: Dexuan Cui <decui@microsoft.com>

Hi Dhiraj,
I checked the code again and it looks like your patch is actually
unnecessary as IMO there is no memory leak here: the 'queue'
pointer is passed to mana_hwc_destroy_wq() as hwc_wq->gdma_wq,
and is later freed in mana_gd_destroy_queue() ->
mana_gd_destroy_queue().

The 'if' test can be removed as the 'err's is always non-zero there.

Thanks,
Dexuan

Re: [PATCH] function mana_hwc_create_wq leaks memory

[Dhiraj Shah]

Hi Dexuan,

Thanks for the feedback.

You are right saying ‘mana_hwc_destroy_wq' free’s up the queue. 

However for example if  function 'mana_hwc_alloc_dma_buf' fails it will goto ‘out' and  call  ‘mana_hwc_destroy_wq', the value 'hwc_wq->gdma_wq' is still not assigned at this point. In the  ‘mana_hwc_destroy_wq' function i see it checks for 'hwc_wq->gdma_wq' before calling, ‘mana_gd_destroy_queue', which makes me think queue is still not freed.

Please let me know if i am missing something.

Regards,
/Dhiraj

> On 10 Jun 2021, at 18:28, Dexuan Cui <decui@microsoft.com> wrote:
> 
>> From: Dexuan Cui <decui@microsoft.com>
>> Sent: Thursday, June 10, 2021 10:18 AM
>> ...
>>> diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c
>>> b/drivers/net/ethernet/microsoft/mana/hw_channel.c
>>> index 1a923fd99990..4aa4bda518fb 100644
>>> --- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
>>> +++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
>>> @@ -501,8 +501,10 @@ static int mana_hwc_create_wq(struct
>>> hw_channel_context *hwc,
>>> 	*hwc_wq_ptr = hwc_wq;
>>> 	return 0;
>>> out:
>>> -	if (err)
>>> +	if (err) {
>> 
>> Here the 'err' must be non-zero. Can you please remove this 'if'?
>> 
>>> +		kfree(queue);
>>> 		mana_hwc_destroy_wq(hwc, hwc_wq);
>>> +	}
>>> 	return err;
>>> }
>> 
>> Reviewed-by: Dexuan Cui <decui@microsoft.com>
> 
> Hi Dhiraj,
> I checked the code again and it looks like your patch is actually
> unnecessary as IMO there is no memory leak here: the 'queue'
> pointer is passed to mana_hwc_destroy_wq() as hwc_wq->gdma_wq,
> and is later freed in mana_gd_destroy_queue() ->
> mana_gd_destroy_queue().
> 
> The 'if' test can be removed as the 'err's is always non-zero there.
> 
> Thanks,
> Dexuan

RE: [PATCH] function mana_hwc_create_wq leaks memory

[Dexuan Cui]

> From: Dhiraj Shah <find.dhiraj@gmail.com>
> Sent: Thursday, June 10, 2021 12:53 PM
>  ...
> Hi Dexuan,
> 
> Thanks for the feedback.
> 
> You are right saying ‘mana_hwc_destroy_wq' free’s up the queue.
> 
> However for example if  function 'mana_hwc_alloc_dma_buf' fails it will goto
> ‘out' and call ‘mana_hwc_destroy_wq', the value 'hwc_wq->gdma_wq' is
> still not assigned at this point. In the  ‘mana_hwc_destroy_wq' function i see

At this point, hwc_wq->gdma_wq stays with its default value NULL.

> it checks for 'hwc_wq->gdma_wq' before calling, ‘mana_gd_destroy_queue',
> which makes me think queue is still not freed.

IMO the current code is not buggy, though I admit it's not very readable. :-)

If you're interested, you're welcome to help make it more readable. I'll also
try to make some time on this.

Thanks,
Dexuan