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Date:   Tue, 27 Mar 2018 08:22:45 -0700
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     Haiyang Zhang <haiyangz@linuxonhyperv.com>
Cc:     haiyangz@microsoft.com, davem@davemloft.net,
        netdev@vger.kernel.org, olaf@aepfle.de, sthemmin@microsoft.com,
        linux-kernel@vger.kernel.org, devel@linuxdriverproject.org,
        vkuznets@redhat.com
Subject: Re: [PATCH net-next, 2/2] hv_netvsc: Add range checking for rx
 packet offset and length
Message-ID: <20180327082245.591612dc@xeon-e3>
In-Reply-To: <20180322190114.25596-3-haiyangz@linuxonhyperv.com>
References: <20180322190114.25596-1-haiyangz@linuxonhyperv.com>
        <20180322190114.25596-3-haiyangz@linuxonhyperv.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Thu, 22 Mar 2018 12:01:14 -0700
Haiyang Zhang <haiyangz@linuxonhyperv.com> wrote:

> From: Haiyang Zhang <haiyangz@microsoft.com>
> 
> This patch adds range checking for rx packet offset and length.
> It may only happen if there is a host side bug.
> 
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> ---
>  drivers/net/hyperv/hyperv_net.h |  1 +
>  drivers/net/hyperv/netvsc.c     | 17 +++++++++++++++--
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index 0db3bd1ea06f..49c05ac894e5 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -793,6 +793,7 @@ struct netvsc_device {
>  
>  	/* Receive buffer allocated by us but manages by NetVSP */
>  	void *recv_buf;
> +	u32 recv_buf_size; /* allocated bytes */
>  	u32 recv_buf_gpadl_handle;
>  	u32 recv_section_cnt;
>  	u32 recv_section_size;
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 1ddb2c39b6e4..a6700d65f206 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -289,6 +289,8 @@ static int netvsc_init_buf(struct hv_device *device,
>  		goto cleanup;
>  	}
>  
> +	net_device->recv_buf_size = buf_size;
> +
>  	/*
>  	 * Establish the gpadl handle for this buffer on this
>  	 * channel.  Note: This call uses the vmbus connection rather
> @@ -1095,11 +1097,22 @@ static int netvsc_receive(struct net_device *ndev,
>  
>  	/* Each range represents 1 RNDIS pkt that contains 1 ethernet frame */
>  	for (i = 0; i < count; i++) {
> -		void *data = recv_buf
> -			+ vmxferpage_packet->ranges[i].byte_offset;
> +		u32 offset = vmxferpage_packet->ranges[i].byte_offset;
>  		u32 buflen = vmxferpage_packet->ranges[i].byte_count;
> +		void *data;
>  		int ret;
>  
> +		if (unlikely(offset + buflen > net_device->recv_buf_size)) {
> +			status = NVSP_STAT_FAIL;
> +			netif_err(net_device_ctx, rx_err, ndev,
> +				  "Packet offset:%u + len:%u too big\n",
> +				  offset, buflen);
> +
> +			continue;
> +		}
> +

If one part of the RNDIS packet is wrong then the whole receive
buffer is damaged. Just return, don't continue.

It could really just be a statistic and a one shot log message.