linux-kernel - Re: [PATCH V2] mlx5: vdpa: fix possible uninitialized var

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Message-ID: <9184ab89-2d64-7f5f-6e16-2f572cc192bc@redhat.com>
Date:   Mon, 18 Jan 2021 13:32:31 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, elic@...dia.com
Subject: Re: [PATCH V2] mlx5: vdpa: fix possible uninitialized var


On 2021/1/17 下午6:30, Michael S. Tsirkin wrote:
> On Thu, Jan 14, 2021 at 03:09:04PM +0800, Jason Wang wrote:
>> When compiling with -Werror=maybe-uninitialized, gcc may complains the
>> possible uninitialized umem. Since the callers won't pass value other
>> than 1 to 3, making 3 as default to fix the compiler warning.
>>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
> Of course if it's actually something else this is not DTRT ...


It breaks some donw stream build (which mandates 
-Werror=maybe-uninitialized)


> As long as we worry about this warning, let's have defence in depth:
>    	case 3:
>    		umem = &mvq->umem3;
>    		break;
>   +	default:
>   +		umem = NULL;
>   +              BUG();
>   +		break;


Checkpatch doesn't like this:

WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code 
rather than BUG() or BUG_ON()
#20: FILE: drivers/vdpa/mlx5/net/mlx5_vnet.c:695:
+        BUG();

But if you stick, I can go this way.

Thanks


>
>> ---
>>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> index f1d54814db97..07ccc61cd6f6 100644
>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> @@ -703,7 +703,7 @@ static void umem_destroy(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue
>>   	case 2:
>>   		umem = &mvq->umem2;
>>   		break;
>> -	case 3:
>> +	default:
>>   		umem = &mvq->umem3;
>>   		break;
>>   	}
>> -- 
>> 2.25.1