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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Haiyang Zhang <haiyangz@linuxonhyperv.com>
Cc:     davem@davemloft.net, netdev@vger.kernel.org,
        haiyangz@microsoft.com, kys@microsoft.com, sthemmin@microsoft.com,
        olaf@aepfle.de, devel@linuxdriverproject.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next,2/2] hv_netvsc: Add range checking for rx packet offset and length
References: <20180322190114.25596-1-haiyangz@linuxonhyperv.com>
        <20180322190114.25596-3-haiyangz@linuxonhyperv.com>
Date:   Fri, 23 Mar 2018 16:17:19 +0100
In-Reply-To: <20180322190114.25596-3-haiyangz@linuxonhyperv.com> (Haiyang
        Zhang's message of "Thu, 22 Mar 2018 12:01:14 -0700")
Message-ID: <87sh8q4y9s.fsf@vitty.brq.redhat.com>
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Haiyang Zhang <haiyangz@linuxonhyperv.com> writes:

> 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);

This shouldn't happen, of course, but I'd rather ratelimit this error or
even used something like netdev_WARN_ONCE().

> +
> +			continue;
> +		}
> +
> +		data = recv_buf + offset;
> +
>  		trace_rndis_recv(ndev, q_idx, data);
>
>  		/* Pass it to the upper layer */

-- 
  Vitaly