netdev - RE: [PATCH v2 net] net: hv_netvsc: fix netvsc_send_completion to avoid multiple message length checks

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Message-ID:
 <BYAPR21MB16886B929DDAAD4970FFDAF0D708A@BYAPR21MB1688.namprd21.prod.outlook.com>
Date: Thu, 3 Aug 2023 00:14:43 +0000
From: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To: Sonia Sharma <sosha@...ux.microsoft.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, Sonia Sharma
	<Sonia.Sharma@...rosoft.com>, KY Srinivasan <kys@...rosoft.com>, Haiyang
 Zhang <haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>, Long Li <longli@...rosoft.com>,
	"davem@...emloft.net" <davem@...emloft.net>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>
Subject: RE: [PATCH v2 net] net: hv_netvsc: fix netvsc_send_completion to
 avoid multiple message length checks

From: Sonia Sharma <sosha@...ux.microsoft.com> Sent: Wednesday, August 2, 2023 2:53 PM
> 
> The switch statement in netvsc_send_completion() is incorrectly validating
> the length of incoming network packets by falling through to the next case.
> Avoid the fallthrough. Instead break after a case match and then process
> the complete() call.
> 
> Signed-off-by: Sonia Sharma <sonia.sharma@...ux.microsoft.com>
> ---
>  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);

Per my previous comment, still need a "return" statement here
so the default error case does not do the memcpy() and complete().

Michael

>  	}
> +
> +	/* 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