[PATCH] function mana_hwc_create_wq leaks memory

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

Signed-off-by: Dhiraj Shah <redacted>
---
 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)

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>

From: Dexuan Cui <decui@microsoft.com>
Sent: Thursday, June 10, 2021 10:18 AM
...

quoted

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'?

quoted

+		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

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 [off-list ref] wrote:

quoted

From: Dexuan Cui <decui@microsoft.com>
Sent: Thursday, June 10, 2021 10:18 AM
...

quoted

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'?

quoted

+		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

From: Dhiraj Shah <redacted>
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