RE: [PATCH] hv_netvsc: fix netvsc_send_completion to avoid multiple message length checks

[Michael Kelley (LINUX)]

From: Sonia Sharma <sosha@xxxxxxxxxxxxxxxxxxx> Sent: Tuesday, August 1, 2023 10:51 PM
> 

The Subject line for networking patches should be tagged
with "net" for fixes to the release that's currently in progress,
or "net-next" for the next release.  Bug fixes like this one can
be "net".   Look through the mailing list archives for examples.

> switch statement in netvsc_send_completion() is incorrectly validating

s/switch/The switch/

> the length of incoming network packets by falling through next case.

s/through next case/through to the next case/

> Avoid the fallthrough, instead break after a case match and then process

s/fallthrough, instead/fallthrough.  Instead,/

> the complete() call.
> 
> Signed-off-by: Sonia Sharma <sonia.sharma@xxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/net/hyperv/netvsc.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 82e9796c8f5e..347688dd2eb9 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -851,7 +851,7 @@ static void netvsc_send_completion(struct net_device *ndev,
>  				   msglen);
>  			return;
>  		}
> -		fallthrough;
> +		break;
> 
>  	case NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE:
>  		if (msglen < sizeof(struct nvsp_message_header) +
> @@ -860,7 +860,7 @@ static void netvsc_send_completion(struct net_device *ndev,
>  				   msglen);
>  			return;
>  		}
> -		fallthrough;
> +		break;
> 
>  	case NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE:
>  		if (msglen < sizeof(struct nvsp_message_header) +
> @@ -869,7 +869,7 @@ static void netvsc_send_completion(struct net_device *ndev,
>  				   msglen);
>  			return;
>  		}
> -		fallthrough;
> +		break;
> 
>  	case NVSP_MSG5_TYPE_SUBCHANNEL:
>  		if (msglen < sizeof(struct nvsp_message_header) +
> @@ -878,10 +878,6 @@ static void netvsc_send_completion(struct net_device *ndev,
>  				   msglen);
>  			return;
>  		}
> -		/* Copy the response back */
> -		memcpy(&net_device->channel_init_pkt, nvsp_packet,
> -		       sizeof(struct nvsp_message));
> -		complete(&net_device->channel_init_wait);
>  		break;
> 
>  	case NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE:
> @@ -904,13 +900,18 @@ static void netvsc_send_completion(struct net_device *ndev,
> 
>  		netvsc_send_tx_complete(ndev, net_device, incoming_channel,
>  					desc, budget);
> -		break;
> +		return;
> 
>  	default:
>  		netdev_err(ndev,
>  			   "Unknown send completion type %d received!!\n",
>  			   nvsp_packet->hdr.msg_type);

Need to add a "return" statement here so that the error case doesn't
try to do the memcpy() and complete().

>  	}
> +
> +	/* Copy the response back */
> +	memcpy(&net_device->channel_init_pkt, nvsp_packet,
> +			sizeof(struct nvsp_message));
> +	complete(&net_device->channel_init_wait);
>  }
> 
>  static u32 netvsc_get_next_send_section(struct netvsc_device *net_device)
> --
> 2.25.1