RE: [PATCH v2] hv_netvsc: Add validation for untrusted Hyper-V values

[Haiyang Zhang]

> -----Original Message-----
> From: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> Sent: Thursday, September 10, 2020 8:48 AM
> To: linux-kernel@xxxxxxxxxxxxxxx
> Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; Wei Liu <wei.liu@xxxxxxxxxx>; linux-
> hyperv@xxxxxxxxxxxxxxx; Andres Beltran <lkmlabelt@xxxxxxxxx>; Michael
> Kelley <mikelley@xxxxxxxxxxxxx>; Saruhan Karademir
> <skarade@xxxxxxxxxxxxx>; Juan Vazquez <juvazq@xxxxxxxxxxxxx>; Andrea
> Parri <parri.andrea@xxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>;
> Jakub Kicinski <kuba@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx
> Subject: [PATCH v2] hv_netvsc: Add validation for untrusted Hyper-V values
> 
> From: Andres Beltran <lkmlabelt@xxxxxxxxx>
> 
> For additional robustness in the face of Hyper-V errors or malicious
> behavior, validate all values that originate from packets that Hyper-V
> has sent to the guest in the host-to-guest ring buffer. Ensure that
> invalid values cannot cause indexing off the end of an array, or
> subvert an existing validation via integer overflow. Ensure that
> outgoing packets do not have any leftover guest memory that has not
> been zeroed out.
> 
> Signed-off-by: Andres Beltran <lkmlabelt@xxxxxxxxx>
> Co-developed-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> ---
> Changes in v2:
>   - Replace size check on struct nvsp_message with sub-checks (Haiyang)
> 
>  drivers/net/hyperv/hyperv_net.h   |   4 +
>  drivers/net/hyperv/netvsc.c       | 120 ++++++++++++++++++++++++++----
>  drivers/net/hyperv/netvsc_drv.c   |   7 ++
>  drivers/net/hyperv/rndis_filter.c |  73 ++++++++++++++++--
>  4 files changed, 184 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h
> b/drivers/net/hyperv/hyperv_net.h
> index 4d2b2d48ff2a1..da78bd0fb2aa2 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -860,6 +860,10 @@ static inline u32 netvsc_rqstor_size(unsigned long
> ringbytes)
>  	       ringbytes / NETVSC_MIN_IN_MSG_SIZE;
>  }
> 
> +#define NETVSC_XFER_HEADER_SIZE(rng_cnt) \
> +		(offsetof(struct vmtransfer_page_packet_header, ranges) +
> \
> +		(rng_cnt) * sizeof(struct vmtransfer_page_range))
> +
>  struct multi_send_data {
>  	struct sk_buff *skb; /* skb containing the pkt */
>  	struct hv_netvsc_packet *pkt; /* netvsc pkt pending */
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 03e93e3ddbad8..90b7a39c2dc78 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -388,6 +388,15 @@ static int netvsc_init_buf(struct hv_device *device,
>  	net_device->recv_section_size = resp->sections[0].sub_alloc_size;
>  	net_device->recv_section_cnt = resp->sections[0].num_sub_allocs;
> 
> +	/* Ensure buffer will not overflow */
> +	if (net_device->recv_section_size < NETVSC_MTU_MIN ||
> (u64)net_device->recv_section_size *
> +	    (u64)net_device->recv_section_cnt > (u64)buf_size) {
> +		netdev_err(ndev, "invalid recv_section_size %u\n",
> +			   net_device->recv_section_size);
> +		ret = -EINVAL;
> +		goto cleanup;
> +	}
> +
>  	/* Setup receive completion ring.
>  	 * Add 1 to the recv_section_cnt because at least one entry in a
>  	 * ring buffer has to be empty.
> @@ -460,6 +469,12 @@ static int netvsc_init_buf(struct hv_device *device,
>  	/* Parse the response */
>  	net_device->send_section_size = init_packet->msg.
> 
> 	v1_msg.send_send_buf_complete.section_size;
> +	if (net_device->send_section_size < NETVSC_MTU_MIN) {
> +		netdev_err(ndev, "invalid send_section_size %u\n",
> +			   net_device->send_section_size);
> +		ret = -EINVAL;
> +		goto cleanup;
> +	}
> 
>  	/* Section count is simply the size divided by the section size. */
>  	net_device->send_section_cnt = buf_size / net_device-
> >send_section_size;
> @@ -740,12 +755,45 @@ static void netvsc_send_completion(struct
> net_device *ndev,
>  				   int budget)
>  {
>  	const struct nvsp_message *nvsp_packet = hv_pkt_data(desc);
> +	u32 msglen = hv_pkt_datalen(desc);
> +
> +	/* Ensure packet is big enough to read header fields */
> +	if (msglen < sizeof(struct nvsp_message_header)) {
> +		netdev_err(ndev, "nvsp_message length too small: %u\n",
> msglen);
> +		return;
> +	}
> 
>  	switch (nvsp_packet->hdr.msg_type) {
>  	case NVSP_MSG_TYPE_INIT_COMPLETE:
> +		if (msglen < sizeof(struct nvsp_message_init_complete)) {

This and other similar places should include header size:
		if (msglen < sizeof(struct nvsp_message_header) + sizeof(struct nvsp_message_init_complete)) {

Thanks,
- Haiyang