Date:   Fri, 9 Apr 2021 15:49:00 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     "Andrea Parri (Microsoft)" <parri.andrea@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        Andres Beltran <lkmlabelt@...il.com>
Subject: RE: [PATCH hyperv-next] Drivers: hv: vmbus: Copy packets sent by
 Hyper-V out of the ring buffer

From: Andrea Parri (Microsoft) <parri.andrea@...il.com> Sent: Thursday, April 8, 2021 9:15 AM
> 
> Pointers to ring-buffer packets sent by Hyper-V are used within the
> guest VM. Hyper-V can send packets with erroneous values or modify
> packet fields after they are processed by the guest. To defend
> against these scenarios, return a copy of the incoming VMBus packet
> after validating its length and offset fields in hv_pkt_iter_first().
> In this way, the packet can no longer be modified by the host.

Andrea -- has anything changed in this version of this patch, except
the value of NETVSC_MAX_XFER_PAGE_RANGES?  It used to be a
fixed 375, but now is NVSP_RSC_MAX, which is 562.

If that's the only change, then

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>

> 
> Signed-off-by: Andres Beltran <lkmlabelt@...il.com>
> Co-developed-by: Andrea Parri (Microsoft) <parri.andrea@...il.com>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@...il.com>
> ---
>  drivers/hv/channel.c              |  9 ++--
>  drivers/hv/hv_fcopy.c             |  1 +
>  drivers/hv/hv_kvp.c               |  1 +
>  drivers/hv/hyperv_vmbus.h         |  2 +-
>  drivers/hv/ring_buffer.c          | 82 ++++++++++++++++++++++++++-----
>  drivers/net/hyperv/hyperv_net.h   |  7 +++
>  drivers/net/hyperv/netvsc.c       |  2 +
>  drivers/net/hyperv/rndis_filter.c |  2 +
>  drivers/scsi/storvsc_drv.c        | 10 ++++
>  include/linux/hyperv.h            | 48 +++++++++++++++---
>  net/vmw_vsock/hyperv_transport.c  |  4 +-
>  11 files changed, 143 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index db30be8f9ccea..b665db21e120d 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -597,12 +597,15 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
>  	newchannel->onchannel_callback = onchannelcallback;
>  	newchannel->channel_callback_context = context;
> 
> -	err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages);
> +	if (!newchannel->max_pkt_size)
> +		newchannel->max_pkt_size = VMBUS_DEFAULT_MAX_PKT_SIZE;
> +
> +	err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages, 0);
>  	if (err)
>  		goto error_clean_ring;
> 
> -	err = hv_ringbuffer_init(&newchannel->inbound,
> -				 &page[send_pages], recv_pages);
> +	err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
> +				 recv_pages, newchannel->max_pkt_size);
>  	if (err)
>  		goto error_clean_ring;
> 
> diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
> index 59ce85e00a028..660036da74495 100644
> --- a/drivers/hv/hv_fcopy.c
> +++ b/drivers/hv/hv_fcopy.c
> @@ -349,6 +349,7 @@ int hv_fcopy_init(struct hv_util_service *srv)
>  {
>  	recv_buffer = srv->recv_buffer;
>  	fcopy_transaction.recv_channel = srv->channel;
> +	fcopy_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
> 
>  	/*
>  	 * When this driver loads, the user level daemon that
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index b49962d312cef..c698592b83e42 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
> @@ -757,6 +757,7 @@ hv_kvp_init(struct hv_util_service *srv)
>  {
>  	recv_buffer = srv->recv_buffer;
>  	kvp_transaction.recv_channel = srv->channel;
> +	kvp_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 4;
> 
>  	/*
>  	 * When this driver loads, the user level daemon that
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 9416e09ebd58c..42f3d9d123a12 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -174,7 +174,7 @@ extern int hv_synic_cleanup(unsigned int cpu);
>  void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
> 
>  int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> -		       struct page *pages, u32 pagecnt);
> +		       struct page *pages, u32 pagecnt, u32 max_pkt_size);
> 
>  void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
> 
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index ecd82ebfd5bc4..848f3bba83f8b 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -190,7 +190,7 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
> 
>  /* Initialize the ring buffer. */
>  int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> -		       struct page *pages, u32 page_cnt)
> +		       struct page *pages, u32 page_cnt, u32 max_pkt_size)
>  {
>  	int i;
>  	struct page **pages_wraparound;
> @@ -232,6 +232,14 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
>  		sizeof(struct hv_ring_buffer);
>  	ring_info->priv_read_index = 0;
> 
> +	/* Initialize buffer that holds copies of incoming packets */
> +	if (max_pkt_size) {
> +		ring_info->pkt_buffer = kzalloc(max_pkt_size, GFP_KERNEL);
> +		if (!ring_info->pkt_buffer)
> +			return -ENOMEM;
> +		ring_info->pkt_buffer_size = max_pkt_size;
> +	}
> +
>  	spin_lock_init(&ring_info->ring_lock);
> 
>  	return 0;
> @@ -244,6 +252,9 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
>  	vunmap(ring_info->ring_buffer);
>  	ring_info->ring_buffer = NULL;
>  	mutex_unlock(&ring_info->ring_buffer_mutex);
> +
> +	kfree(ring_info->pkt_buffer);
> +	ring_info->pkt_buffer_size = 0;
>  }
> 
>  /* Write to the ring buffer. */
> @@ -384,7 +395,7 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
>  	memcpy(buffer, (const char *)desc + offset, packetlen);
> 
>  	/* Advance ring index to next packet descriptor */
> -	__hv_pkt_iter_next(channel, desc);
> +	__hv_pkt_iter_next(channel, desc, true);
> 
>  	/* Notify host of update */
>  	hv_pkt_iter_close(channel);
> @@ -410,6 +421,22 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
>  		return (rbi->ring_datasize - priv_read_loc) + write_loc;
>  }
> 
> +/*
> + * Get first vmbus packet without copying it out of the ring buffer
> + */
> +struct vmpacket_descriptor *hv_pkt_iter_first_raw(struct vmbus_channel *channel)
> +{
> +	struct hv_ring_buffer_info *rbi = &channel->inbound;
> +
> +	hv_debug_delay_test(channel, MESSAGE_DELAY);
> +
> +	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
> +		return NULL;
> +
> +	return (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi-
> >priv_read_index);
> +}
> +EXPORT_SYMBOL_GPL(hv_pkt_iter_first_raw);
> +
>  /*
>   * Get first vmbus packet from ring buffer after read_index
>   *
> @@ -418,17 +445,49 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
>  struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
>  {
>  	struct hv_ring_buffer_info *rbi = &channel->inbound;
> -	struct vmpacket_descriptor *desc;
> +	struct vmpacket_descriptor *desc, *desc_copy;
> +	u32 bytes_avail, pkt_len, pkt_offset;
> 
> -	hv_debug_delay_test(channel, MESSAGE_DELAY);
> -	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
> +	desc = hv_pkt_iter_first_raw(channel);
> +	if (!desc)
>  		return NULL;
> 
> -	desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index;
> -	if (desc)
> -		prefetch((char *)desc + (desc->len8 << 3));
> +	bytes_avail = min(rbi->pkt_buffer_size, hv_pkt_iter_avail(rbi));
> +
> +	/*
> +	 * Ensure the compiler does not use references to incoming Hyper-V values (which
> +	 * could change at any moment) when reading local variables later in the code
> +	 */
> +	pkt_len = READ_ONCE(desc->len8) << 3;
> +	pkt_offset = READ_ONCE(desc->offset8) << 3;
> +
> +	/*
> +	 * If pkt_len is invalid, set it to the smaller of hv_pkt_iter_avail() and
> +	 * rbi->pkt_buffer_size
> +	 */
> +	if (pkt_len < sizeof(struct vmpacket_descriptor) || pkt_len > bytes_avail)
> +		pkt_len = bytes_avail;
> +
> +	/*
> +	 * If pkt_offset is invalid, arbitrarily set it to
> +	 * the size of vmpacket_descriptor
> +	 */
> +	if (pkt_offset < sizeof(struct vmpacket_descriptor) || pkt_offset > pkt_len)
> +		pkt_offset = sizeof(struct vmpacket_descriptor);
> +
> +	/* Copy the Hyper-V packet out of the ring buffer */
> +	desc_copy = (struct vmpacket_descriptor *)rbi->pkt_buffer;
> +	memcpy(desc_copy, desc, pkt_len);
> +
> +	/*
> +	 * Hyper-V could still change len8 and offset8 after the earlier read.
> +	 * Ensure that desc_copy has legal values for len8 and offset8 that
> +	 * are consistent with the copy we just made
> +	 */
> +	desc_copy->len8 = pkt_len >> 3;
> +	desc_copy->offset8 = pkt_offset >> 3;
> 
> -	return desc;
> +	return desc_copy;
>  }
>  EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
> 
> @@ -440,7 +499,8 @@ EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
>   */
>  struct vmpacket_descriptor *
>  __hv_pkt_iter_next(struct vmbus_channel *channel,
> -		   const struct vmpacket_descriptor *desc)
> +		   const struct vmpacket_descriptor *desc,
> +		   bool copy)
>  {
>  	struct hv_ring_buffer_info *rbi = &channel->inbound;
>  	u32 packetlen = desc->len8 << 3;
> @@ -453,7 +513,7 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
>  		rbi->priv_read_index -= dsize;
> 
>  	/* more data? */
> -	return hv_pkt_iter_first(channel);
> +	return copy ? hv_pkt_iter_first(channel) : hv_pkt_iter_first_raw(channel);
>  }
>  EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index e1a497d3c9ba4..154539b2f75ba 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -895,9 +895,16 @@ static inline u32 netvsc_rqstor_size(unsigned long ringbytes)
>  		ringbytes / NETVSC_MIN_IN_MSG_SIZE;
>  }
> 
> +/* XFER PAGE packets can specify a maximum of 375 ranges for NDIS >= 6.0
> + * and a maximum of 64 ranges for NDIS < 6.0 with no RSC; with RSC, this
> + * limit is raised to 562 (= NVSP_RSC_MAX).
> + */
> +#define NETVSC_MAX_XFER_PAGE_RANGES NVSP_RSC_MAX
>  #define NETVSC_XFER_HEADER_SIZE(rng_cnt) \
>  		(offsetof(struct vmtransfer_page_packet_header, ranges) + \
>  		(rng_cnt) * sizeof(struct vmtransfer_page_range))
> +#define NETVSC_MAX_PKT_SIZE
> (NETVSC_XFER_HEADER_SIZE(NETVSC_MAX_XFER_PAGE_RANGES) + \
> +		sizeof(struct nvsp_message) + (sizeof(u32) * VRSS_SEND_TAB_SIZE))
> 
>  struct multi_send_data {
>  	struct sk_buff *skb; /* skb containing the pkt */
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index c64cc7639c39c..d17ff04986f52 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -1603,6 +1603,8 @@ struct netvsc_device *netvsc_device_add(struct hv_device
> *device,
> 
>  	/* Open the channel */
>  	device->channel->rqstor_size = netvsc_rqstor_size(netvsc_ring_bytes);
> +	device->channel->max_pkt_size = NETVSC_MAX_PKT_SIZE;
> +
>  	ret = vmbus_open(device->channel, netvsc_ring_bytes,
>  			 netvsc_ring_bytes,  NULL, 0,
>  			 netvsc_channel_cb, net_device->chan_table);
> diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
> index 123cc9d25f5ed..6508c4724c224 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -1260,6 +1260,8 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
>  	nvchan->channel = new_sc;
> 
>  	new_sc->rqstor_size = netvsc_rqstor_size(netvsc_ring_bytes);
> +	new_sc->max_pkt_size = NETVSC_MAX_PKT_SIZE;
> +
>  	ret = vmbus_open(new_sc, netvsc_ring_bytes,
>  			 netvsc_ring_bytes, NULL, 0,
>  			 netvsc_channel_cb, nvchan);
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 6bc5453cea8a7..bfbaebded8025 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -402,6 +402,14 @@ static void storvsc_on_channel_callback(void *context);
>  #define STORVSC_IDE_MAX_TARGETS				1
>  #define STORVSC_IDE_MAX_CHANNELS			1
> 
> +/*
> + * Upper bound on the size of a storvsc packet. vmscsi_size_delta is not
> + * included in the calculation because it is set after STORVSC_MAX_PKT_SIZE
> + * is used in storvsc_connect_to_vsp
> + */
> +#define STORVSC_MAX_PKT_SIZE (sizeof(struct vmpacket_descriptor) +\
> +			      sizeof(struct vstor_packet))
> +
>  struct storvsc_cmd_request {
>  	struct scsi_cmnd *cmd;
> 
> @@ -697,6 +705,7 @@ static void handle_sc_creation(struct vmbus_channel *new_sc)
>  		return;
> 
>  	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
> +	new_sc->max_pkt_size = STORVSC_MAX_PKT_SIZE;
> 
>  	/*
>  	 * The size of vmbus_requestor is an upper bound on the number of requests
> @@ -1290,6 +1299,7 @@ static int storvsc_connect_to_vsp(struct hv_device *device, u32
> ring_size,
> 
>  	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
> 
> +	device->channel->max_pkt_size = STORVSC_MAX_PKT_SIZE;
>  	/*
>  	 * The size of vmbus_requestor is an upper bound on the number of requests
>  	 * that can be in-progress at any one time across all channels.
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 2c18c8e768efe..7387bb41f6a37 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -181,6 +181,10 @@ struct hv_ring_buffer_info {
>  	 * being freed while the ring buffer is being accessed.
>  	 */
>  	struct mutex ring_buffer_mutex;
> +
> +	/* Buffer that holds a copy of an incoming host packet */
> +	void *pkt_buffer;
> +	u32 pkt_buffer_size;
>  };
> 
> 
> @@ -788,6 +792,8 @@ struct vmbus_device {
>  	bool allowed_in_isolated;
>  };
> 
> +#define VMBUS_DEFAULT_MAX_PKT_SIZE 4096
> +
>  struct vmbus_channel {
>  	struct list_head listentry;
> 
> @@ -1010,6 +1016,9 @@ struct vmbus_channel {
>  	/* request/transaction ids for VMBus */
>  	struct vmbus_requestor requestor;
>  	u32 rqstor_size;
> +
> +	/* The max size of a packet on this channel */
> +	u32 max_pkt_size;
>  };
> 
>  u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr);
> @@ -1651,32 +1660,55 @@ static inline u32 hv_pkt_datalen(const struct
> vmpacket_descriptor *desc)
>  }
> 
> 
> +struct vmpacket_descriptor *
> +hv_pkt_iter_first_raw(struct vmbus_channel *channel);
> +
>  struct vmpacket_descriptor *
>  hv_pkt_iter_first(struct vmbus_channel *channel);
> 
>  struct vmpacket_descriptor *
>  __hv_pkt_iter_next(struct vmbus_channel *channel,
> -		   const struct vmpacket_descriptor *pkt);
> +		   const struct vmpacket_descriptor *pkt,
> +		   bool copy);
> 
>  void hv_pkt_iter_close(struct vmbus_channel *channel);
> 
> -/*
> - * Get next packet descriptor from iterator
> - * If at end of list, return NULL and update host.
> - */
>  static inline struct vmpacket_descriptor *
> -hv_pkt_iter_next(struct vmbus_channel *channel,
> -		 const struct vmpacket_descriptor *pkt)
> +hv_pkt_iter_next_pkt(struct vmbus_channel *channel,
> +		     const struct vmpacket_descriptor *pkt,
> +		     bool copy)
>  {
>  	struct vmpacket_descriptor *nxt;
> 
> -	nxt = __hv_pkt_iter_next(channel, pkt);
> +	nxt = __hv_pkt_iter_next(channel, pkt, copy);
>  	if (!nxt)
>  		hv_pkt_iter_close(channel);
> 
>  	return nxt;
>  }
> 
> +/*
> + * Get next packet descriptor without copying it out of the ring buffer
> + * If at end of list, return NULL and update host.
> + */
> +static inline struct vmpacket_descriptor *
> +hv_pkt_iter_next_raw(struct vmbus_channel *channel,
> +		     const struct vmpacket_descriptor *pkt)
> +{
> +	return hv_pkt_iter_next_pkt(channel, pkt, false);
> +}
> +
> +/*
> + * Get next packet descriptor from iterator
> + * If at end of list, return NULL and update host.
> + */
> +static inline struct vmpacket_descriptor *
> +hv_pkt_iter_next(struct vmbus_channel *channel,
> +		 const struct vmpacket_descriptor *pkt)
> +{
> +	return hv_pkt_iter_next_pkt(channel, pkt, true);
> +}
> +
>  #define foreach_vmbus_pkt(pkt, channel) \
>  	for (pkt = hv_pkt_iter_first(channel); pkt; \
>  	    pkt = hv_pkt_iter_next(channel, pkt))
> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
> index cc3bae2659e79..19189cf30a72f 100644
> --- a/net/vmw_vsock/hyperv_transport.c
> +++ b/net/vmw_vsock/hyperv_transport.c
> @@ -596,7 +596,7 @@ static ssize_t hvs_stream_dequeue(struct vsock_sock *vsk, struct
> msghdr *msg,
>  		return -EOPNOTSUPP;
> 
>  	if (need_refill) {
> -		hvs->recv_desc = hv_pkt_iter_first(hvs->chan);
> +		hvs->recv_desc = hv_pkt_iter_first_raw(hvs->chan);
>  		ret = hvs_update_recv_data(hvs);
>  		if (ret)
>  			return ret;
> @@ -610,7 +610,7 @@ static ssize_t hvs_stream_dequeue(struct vsock_sock *vsk, struct
> msghdr *msg,
> 
>  	hvs->recv_data_len -= to_read;
>  	if (hvs->recv_data_len == 0) {
> -		hvs->recv_desc = hv_pkt_iter_next(hvs->chan, hvs->recv_desc);
> +		hvs->recv_desc = hv_pkt_iter_next_raw(hvs->chan, hvs->recv_desc);
>  		if (hvs->recv_desc) {
>  			ret = hvs_update_recv_data(hvs);
>  			if (ret)
> --
> 2.25.1

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