[PATCH net, 0/2] Fix send indirection table offset

[PATCH net, 0/2] Fix send indirection table offset

[Haiyang Zhang]

Fix send indirection table offset issues related to guest and
host bugs.


Haiyang Zhang (2):
  hv_netvsc: Fix offset usage in netvsc_send_table()
  hv_netvsc: Fix send_table offset in case of a host bug

 drivers/net/hyperv/hyperv_net.h |  3 ++-
 drivers/net/hyperv/netvsc.c     | 35 +++++++++++++++++++++++++++--------
 2 files changed, 29 insertions(+), 9 deletions(-)

-- 
1.8.3.1

[PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()

[Haiyang Zhang]

To reach the data region, the existing code adds offset in struct
nvsp_5_send_indirect_table on the beginning of this struct. But the
offset should be based on the beginning of its container,
struct nvsp_message. This bug causes the first table entry missing,
and adds an extra zero from the zero pad after the data region.
This can put extra burden on the channel 0.

So, correct the offset usage. Also add a boundary check to ensure
not reading beyond data region.

Fixes: 5b54dac856cb ("hyperv: Add support for virtual Receive Side Scaling (vRSS)")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 drivers/net/hyperv/hyperv_net.h |  3 ++-
 drivers/net/hyperv/netvsc.c     | 26 ++++++++++++++++++--------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 670ef68..fb547f3 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -609,7 +609,8 @@ struct nvsp_5_send_indirect_table {
 	/* The number of entries in the send indirection table */
 	u32 count;
 
-	/* The offset of the send indirection table from top of this struct.
+	/* The offset of the send indirection table from the beginning of
+	 * struct nvsp_message.
 	 * The send indirection table tells which channel to put the send
 	 * traffic on. Each entry is a channel number.
 	 */
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index d22a36f..efd30e2 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1178,20 +1178,28 @@ static int netvsc_receive(struct net_device *ndev,
 }
 
 static void netvsc_send_table(struct net_device *ndev,
-			      const struct nvsp_message *nvmsg)
+			      const struct nvsp_message *nvmsg,
+			      u32 msglen)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(ndev);
-	u32 count, *tab;
+	u32 count, offset, *tab;
 	int i;
 
 	count = nvmsg->msg.v5_msg.send_table.count;
+	offset = nvmsg->msg.v5_msg.send_table.offset;
+
 	if (count != VRSS_SEND_TAB_SIZE) {
 		netdev_err(ndev, "Received wrong send-table size:%u\n", count);
 		return;
 	}
 
-	tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
-		      nvmsg->msg.v5_msg.send_table.offset);
+	if (offset + count * sizeof(u32) > msglen) {
+		netdev_err(ndev, "Received send-table offset too big:%u\n",
+			   offset);
+		return;
+	}
+
+	tab = (void *)nvmsg + offset;
 
 	for (i = 0; i < count; i++)
 		net_device_ctx->tx_table[i] = tab[i];
@@ -1209,12 +1217,13 @@ static void netvsc_send_vf(struct net_device *ndev,
 		    net_device_ctx->vf_alloc ? "added" : "removed");
 }
 
-static  void netvsc_receive_inband(struct net_device *ndev,
-				   const struct nvsp_message *nvmsg)
+static void netvsc_receive_inband(struct net_device *ndev,
+				  const struct nvsp_message *nvmsg,
+				  u32 msglen)
 {
 	switch (nvmsg->hdr.msg_type) {
 	case NVSP_MSG5_TYPE_SEND_INDIRECTION_TABLE:
-		netvsc_send_table(ndev, nvmsg);
+		netvsc_send_table(ndev, nvmsg, msglen);
 		break;
 
 	case NVSP_MSG4_TYPE_SEND_VF_ASSOCIATION:
@@ -1232,6 +1241,7 @@ static int netvsc_process_raw_pkt(struct hv_device *device,
 {
 	struct vmbus_channel *channel = nvchan->channel;
 	const struct nvsp_message *nvmsg = hv_pkt_data(desc);
+	u32 msglen = hv_pkt_datalen(desc);
 
 	trace_nvsp_recv(ndev, channel, nvmsg);
 
@@ -1247,7 +1257,7 @@ static int netvsc_process_raw_pkt(struct hv_device *device,
 		break;
 
 	case VM_PKT_DATA_INBAND:
-		netvsc_receive_inband(ndev, nvmsg);
+		netvsc_receive_inband(ndev, nvmsg, msglen);
 		break;
 
 	default:
-- 
1.8.3.1

[PATCH net, 2/2] hv_netvsc: Fix send_table offset in case of a host bug

[Haiyang Zhang]

If negotiated NVSP version <= NVSP_PROTOCOL_VERSION_6, the offset may
be wrong (too small) due to a host bug. This can cause missing the
end of the send indirection table, and add multiple zero entries from
leading zeros before the data region. This bug adds extra burden on
channel 0.

So fix the offset by computing it from the end of the table. This
will ensure netvsc driver runs normally on unfixed hosts, and future
fixed hosts.

Fixes: 5b54dac856cb ("hyperv: Add support for virtual Receive Side Scaling (vRSS)")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 drivers/net/hyperv/netvsc.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index efd30e2..7c5481a 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1178,6 +1178,7 @@ static int netvsc_receive(struct net_device *ndev,
 }
 
 static void netvsc_send_table(struct net_device *ndev,
+			      struct netvsc_device *nvscdev,
 			      const struct nvsp_message *nvmsg,
 			      u32 msglen)
 {
@@ -1193,6 +1194,13 @@ static void netvsc_send_table(struct net_device *ndev,
 		return;
 	}
 
+	/* If negotiated version <= NVSP_PROTOCOL_VERSION_6, the offset may be
+	 * wrong due to a host bug. So fix the offset here.
+	 */
+	if (nvscdev->nvsp_version <= NVSP_PROTOCOL_VERSION_6)
+		offset = msglen - count * sizeof(u32);
+
+	/* Boundary check for all versions */
 	if (offset + count * sizeof(u32) > msglen) {
 		netdev_err(ndev, "Received send-table offset too big:%u\n",
 			   offset);
@@ -1218,12 +1226,13 @@ static void netvsc_send_vf(struct net_device *ndev,
 }
 
 static void netvsc_receive_inband(struct net_device *ndev,
+				  struct netvsc_device *nvscdev,
 				  const struct nvsp_message *nvmsg,
 				  u32 msglen)
 {
 	switch (nvmsg->hdr.msg_type) {
 	case NVSP_MSG5_TYPE_SEND_INDIRECTION_TABLE:
-		netvsc_send_table(ndev, nvmsg, msglen);
+		netvsc_send_table(ndev, nvscdev, nvmsg, msglen);
 		break;
 
 	case NVSP_MSG4_TYPE_SEND_VF_ASSOCIATION:
@@ -1257,7 +1266,7 @@ static int netvsc_process_raw_pkt(struct hv_device *device,
 		break;
 
 	case VM_PKT_DATA_INBAND:
-		netvsc_receive_inband(ndev, nvmsg, msglen);
+		netvsc_receive_inband(ndev, net_device, nvmsg, msglen);
 		break;
 
 	default:
-- 
1.8.3.1

Re: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()

[Vitaly Kuznetsov]

Haiyang Zhang <haiyangz@microsoft.com> writes:

> To reach the data region, the existing code adds offset in struct
> nvsp_5_send_indirect_table on the beginning of this struct. But the
> offset should be based on the beginning of its container,
> struct nvsp_message. This bug causes the first table entry missing,
> and adds an extra zero from the zero pad after the data region.
> This can put extra burden on the channel 0.
>
> So, correct the offset usage. Also add a boundary check to ensure
> not reading beyond data region.
>
> Fixes: 5b54dac856cb ("hyperv: Add support for virtual Receive Side Scaling (vRSS)")
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> ---
>  drivers/net/hyperv/hyperv_net.h |  3 ++-
>  drivers/net/hyperv/netvsc.c     | 26 ++++++++++++++++++--------
>  2 files changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index 670ef68..fb547f3 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -609,7 +609,8 @@ struct nvsp_5_send_indirect_table {
>  	/* The number of entries in the send indirection table */
>  	u32 count;
>  
> -	/* The offset of the send indirection table from top of this struct.
> +	/* The offset of the send indirection table from the beginning of
> +	 * struct nvsp_message.
>  	 * The send indirection table tells which channel to put the send
>  	 * traffic on. Each entry is a channel number.
>  	 */
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index d22a36f..efd30e2 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -1178,20 +1178,28 @@ static int netvsc_receive(struct net_device *ndev,
>  }
>  
>  static void netvsc_send_table(struct net_device *ndev,
> -			      const struct nvsp_message *nvmsg)
> +			      const struct nvsp_message *nvmsg,
> +			      u32 msglen)
>  {
>  	struct net_device_context *net_device_ctx = netdev_priv(ndev);
> -	u32 count, *tab;
> +	u32 count, offset, *tab;
>  	int i;
>  
>  	count = nvmsg->msg.v5_msg.send_table.count;
> +	offset = nvmsg->msg.v5_msg.send_table.offset;
> +
>  	if (count != VRSS_SEND_TAB_SIZE) {
>  		netdev_err(ndev, "Received wrong send-table size:%u\n", count);
>  		return;
>  	}
>  
> -	tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
> -		      nvmsg->msg.v5_msg.send_table.offset);
> +	if (offset + count * sizeof(u32) > msglen) {

Nit: I think this can overflow.

> +		netdev_err(ndev, "Received send-table offset too big:%u\n",
> +			   offset);
> +		return;
> +	}
> +
> +	tab = (void *)nvmsg + offset;

But tab is 'u32 *', doesn't compiler complain?

>  
>  	for (i = 0; i < count; i++)
>  		net_device_ctx->tx_table[i] = tab[i];
> @@ -1209,12 +1217,13 @@ static void netvsc_send_vf(struct net_device *ndev,
>  		    net_device_ctx->vf_alloc ? "added" : "removed");
>  }
>  
> -static  void netvsc_receive_inband(struct net_device *ndev,
> -				   const struct nvsp_message *nvmsg)
> +static void netvsc_receive_inband(struct net_device *ndev,
> +				  const struct nvsp_message *nvmsg,
> +				  u32 msglen)
>  {
>  	switch (nvmsg->hdr.msg_type) {
>  	case NVSP_MSG5_TYPE_SEND_INDIRECTION_TABLE:
> -		netvsc_send_table(ndev, nvmsg);
> +		netvsc_send_table(ndev, nvmsg, msglen);
>  		break;
>  
>  	case NVSP_MSG4_TYPE_SEND_VF_ASSOCIATION:
> @@ -1232,6 +1241,7 @@ static int netvsc_process_raw_pkt(struct hv_device *device,
>  {
>  	struct vmbus_channel *channel = nvchan->channel;
>  	const struct nvsp_message *nvmsg = hv_pkt_data(desc);
> +	u32 msglen = hv_pkt_datalen(desc);
>  
>  	trace_nvsp_recv(ndev, channel, nvmsg);
>  
> @@ -1247,7 +1257,7 @@ static int netvsc_process_raw_pkt(struct hv_device *device,
>  		break;
>  
>  	case VM_PKT_DATA_INBAND:
> -		netvsc_receive_inband(ndev, nvmsg);
> +		netvsc_receive_inband(ndev, nvmsg, msglen);
>  		break;
>  
>  	default:

-- 
Vitaly

Re: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()

[Stephen Hemminger]

On Mon, 18 Nov 2019 18:28:48 +0100
Vitaly Kuznetsov <vkuznets@redhat.com> wrote:

> > +		netdev_err(ndev, "Received send-table offset too big:%u\n",
> > +			   offset);
> > +		return;
> > +	}
> > +
> > +	tab = (void *)nvmsg + offset;  
> 
> But tab is 'u32 *', doesn't compiler complain?

nvmsg + offset is still of type void *.
assigning void * to another pointer type is allowed with C.

RE: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()

[Haiyang Zhang]

> -----Original Message-----
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
> Sent: Monday, November 18, 2019 12:29 PM
> To: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: KY Srinivasan <kys@microsoft.com>; Stephen Hemminger
> <sthemmin@microsoft.com>; olaf@aepfle.de; davem@davemloft.net; linux-
> kernel@vger.kernel.org; sashal@kernel.org; linux-hyperv@vger.kernel.org;
> netdev@vger.kernel.org
> Subject: Re: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()
> 
> Haiyang Zhang <haiyangz@microsoft.com> writes:
> 
> > To reach the data region, the existing code adds offset in struct
> > nvsp_5_send_indirect_table on the beginning of this struct. But the
> > offset should be based on the beginning of its container,
> > struct nvsp_message. This bug causes the first table entry missing,
> > and adds an extra zero from the zero pad after the data region.
> > This can put extra burden on the channel 0.
> >
> > So, correct the offset usage. Also add a boundary check to ensure
> > not reading beyond data region.
> >
> > Fixes: 5b54dac856cb ("hyperv: Add support for virtual Receive Side Scaling
> (vRSS)")
> > Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> > ---
> >  drivers/net/hyperv/hyperv_net.h |  3 ++-
> >  drivers/net/hyperv/netvsc.c     | 26 ++++++++++++++++++--------
> >  2 files changed, 20 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/hyperv_net.h
> b/drivers/net/hyperv/hyperv_net.h
> > index 670ef68..fb547f3 100644
> > --- a/drivers/net/hyperv/hyperv_net.h
> > +++ b/drivers/net/hyperv/hyperv_net.h
> > @@ -609,7 +609,8 @@ struct nvsp_5_send_indirect_table {
> >  	/* The number of entries in the send indirection table */
> >  	u32 count;
> >
> > -	/* The offset of the send indirection table from top of this struct.
> > +	/* The offset of the send indirection table from the beginning of
> > +	 * struct nvsp_message.
> >  	 * The send indirection table tells which channel to put the send
> >  	 * traffic on. Each entry is a channel number.
> >  	 */
> > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > index d22a36f..efd30e2 100644
> > --- a/drivers/net/hyperv/netvsc.c
> > +++ b/drivers/net/hyperv/netvsc.c
> > @@ -1178,20 +1178,28 @@ static int netvsc_receive(struct net_device *ndev,
> >  }
> >
> >  static void netvsc_send_table(struct net_device *ndev,
> > -			      const struct nvsp_message *nvmsg)
> > +			      const struct nvsp_message *nvmsg,
> > +			      u32 msglen)
> >  {
> >  	struct net_device_context *net_device_ctx = netdev_priv(ndev);
> > -	u32 count, *tab;
> > +	u32 count, offset, *tab;
> >  	int i;
> >
> >  	count = nvmsg->msg.v5_msg.send_table.count;
> > +	offset = nvmsg->msg.v5_msg.send_table.offset;
> > +
> >  	if (count != VRSS_SEND_TAB_SIZE) {
> >  		netdev_err(ndev, "Received wrong send-table size:%u\n",
> count);
> >  		return;
> >  	}
> >
> > -	tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
> > -		      nvmsg->msg.v5_msg.send_table.offset);
> > +	if (offset + count * sizeof(u32) > msglen) {
> 
> Nit: I think this can overflow.

To prevent overflow, I will change it to:
	if (offset > msglen || offset + count * sizeof(u32) > msglen) {
Thanks,
- Haiyang

RE: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()

[Michael Kelley]

From: Haiyang Zhang <haiyangz@microsoft.com> Sent: Monday, November 18, 2019 10:40 AM
> > -----Original Message-----
> > From: Vitaly Kuznetsov <vkuznets@redhat.com>
> > Sent: Monday, November 18, 2019 12:29 PM
> >
> > Haiyang Zhang <haiyangz@microsoft.com> writes:
> >
> > > To reach the data region, the existing code adds offset in struct
> > > nvsp_5_send_indirect_table on the beginning of this struct. But the
> > > offset should be based on the beginning of its container,
> > > struct nvsp_message. This bug causes the first table entry missing,
> > > and adds an extra zero from the zero pad after the data region.
> > > This can put extra burden on the channel 0.
> > >
> > > So, correct the offset usage. Also add a boundary check to ensure
> > > not reading beyond data region.
> > >
> > > Fixes: 5b54dac856cb ("hyperv: Add support for virtual Receive Side Scaling
> > (vRSS)")
> > > Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> > > ---
> > >  drivers/net/hyperv/hyperv_net.h |  3 ++-
> > >  drivers/net/hyperv/netvsc.c     | 26 ++++++++++++++++++--------
> > >  2 files changed, 20 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/hyperv/hyperv_net.h
> > b/drivers/net/hyperv/hyperv_net.h
> > > index 670ef68..fb547f3 100644
> > > --- a/drivers/net/hyperv/hyperv_net.h
> > > +++ b/drivers/net/hyperv/hyperv_net.h
> > > @@ -609,7 +609,8 @@ struct nvsp_5_send_indirect_table {
> > >  	/* The number of entries in the send indirection table */
> > >  	u32 count;
> > >
> > > -	/* The offset of the send indirection table from top of this struct.
> > > +	/* The offset of the send indirection table from the beginning of
> > > +	 * struct nvsp_message.
> > >  	 * The send indirection table tells which channel to put the send
> > >  	 * traffic on. Each entry is a channel number.
> > >  	 */
> > > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > > index d22a36f..efd30e2 100644
> > > --- a/drivers/net/hyperv/netvsc.c
> > > +++ b/drivers/net/hyperv/netvsc.c
> > > @@ -1178,20 +1178,28 @@ static int netvsc_receive(struct net_device *ndev,
> > >  }
> > >
> > >  static void netvsc_send_table(struct net_device *ndev,
> > > -			      const struct nvsp_message *nvmsg)
> > > +			      const struct nvsp_message *nvmsg,
> > > +			      u32 msglen)
> > >  {
> > >  	struct net_device_context *net_device_ctx = netdev_priv(ndev);
> > > -	u32 count, *tab;
> > > +	u32 count, offset, *tab;
> > >  	int i;
> > >
> > >  	count = nvmsg->msg.v5_msg.send_table.count;
> > > +	offset = nvmsg->msg.v5_msg.send_table.offset;
> > > +
> > >  	if (count != VRSS_SEND_TAB_SIZE) {
> > >  		netdev_err(ndev, "Received wrong send-table size:%u\n",
> > count);
> > >  		return;
> > >  	}
> > >
> > > -	tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
> > > -		      nvmsg->msg.v5_msg.send_table.offset);
> > > +	if (offset + count * sizeof(u32) > msglen) {
> >
> > Nit: I think this can overflow.
> 
> To prevent overflow, I will change it to:
> 	if (offset > msglen || offset + count * sizeof(u32) > msglen) {
> Thanks,
> - Haiyang

Actually, this would be simpler since we already trust msglen and count
to have good values:

	if (offset > msglen - count * sizeof(u32)) {

Michael

RE: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()

[Haiyang Zhang]

> -----Original Message-----
> From: Michael Kelley <mikelley@microsoft.com>
> Sent: Monday, November 18, 2019 3:47 PM
> To: Haiyang Zhang <haiyangz@microsoft.com>; vkuznets
> <vkuznets@redhat.com>
> Cc: KY Srinivasan <kys@microsoft.com>; Stephen Hemminger
> <sthemmin@microsoft.com>; olaf@aepfle.de; davem@davemloft.net; linux-
> kernel@vger.kernel.org; sashal@kernel.org; linux-hyperv@vger.kernel.org;
> netdev@vger.kernel.org
> Subject: RE: [PATCH net, 1/2] hv_netvsc: Fix offset usage in netvsc_send_table()
> 
> From: Haiyang Zhang <haiyangz@microsoft.com> Sent: Monday, November 18,
> 2019 10:40 AM
> > > -----Original Message-----
> > > From: Vitaly Kuznetsov <vkuznets@redhat.com>
> > > Sent: Monday, November 18, 2019 12:29 PM
> > >
> > > Haiyang Zhang <haiyangz@microsoft.com> writes:
> > >
> > > > To reach the data region, the existing code adds offset in struct
> > > > nvsp_5_send_indirect_table on the beginning of this struct. But the
> > > > offset should be based on the beginning of its container,
> > > > struct nvsp_message. This bug causes the first table entry missing,
> > > > and adds an extra zero from the zero pad after the data region.
> > > > This can put extra burden on the channel 0.
> > > >
> > > > So, correct the offset usage. Also add a boundary check to ensure
> > > > not reading beyond data region.
> > > >
> > > > Fixes: 5b54dac856cb ("hyperv: Add support for virtual Receive Side
> Scaling
> > > (vRSS)")
> > > > Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> > > > ---
> > > >  drivers/net/hyperv/hyperv_net.h |  3 ++-
> > > >  drivers/net/hyperv/netvsc.c     | 26 ++++++++++++++++++--------
> > > >  2 files changed, 20 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/net/hyperv/hyperv_net.h
> > > b/drivers/net/hyperv/hyperv_net.h
> > > > index 670ef68..fb547f3 100644
> > > > --- a/drivers/net/hyperv/hyperv_net.h
> > > > +++ b/drivers/net/hyperv/hyperv_net.h
> > > > @@ -609,7 +609,8 @@ struct nvsp_5_send_indirect_table {
> > > >  	/* The number of entries in the send indirection table */
> > > >  	u32 count;
> > > >
> > > > -	/* The offset of the send indirection table from top of this struct.
> > > > +	/* The offset of the send indirection table from the beginning of
> > > > +	 * struct nvsp_message.
> > > >  	 * The send indirection table tells which channel to put the send
> > > >  	 * traffic on. Each entry is a channel number.
> > > >  	 */
> > > > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > > > index d22a36f..efd30e2 100644
> > > > --- a/drivers/net/hyperv/netvsc.c
> > > > +++ b/drivers/net/hyperv/netvsc.c
> > > > @@ -1178,20 +1178,28 @@ static int netvsc_receive(struct net_device
> *ndev,
> > > >  }
> > > >
> > > >  static void netvsc_send_table(struct net_device *ndev,
> > > > -			      const struct nvsp_message *nvmsg)
> > > > +			      const struct nvsp_message *nvmsg,
> > > > +			      u32 msglen)
> > > >  {
> > > >  	struct net_device_context *net_device_ctx = netdev_priv(ndev);
> > > > -	u32 count, *tab;
> > > > +	u32 count, offset, *tab;
> > > >  	int i;
> > > >
> > > >  	count = nvmsg->msg.v5_msg.send_table.count;
> > > > +	offset = nvmsg->msg.v5_msg.send_table.offset;
> > > > +
> > > >  	if (count != VRSS_SEND_TAB_SIZE) {
> > > >  		netdev_err(ndev, "Received wrong send-table size:%u\n",
> > > count);
> > > >  		return;
> > > >  	}
> > > >
> > > > -	tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
> > > > -		      nvmsg->msg.v5_msg.send_table.offset);
> > > > +	if (offset + count * sizeof(u32) > msglen) {
> > >
> > > Nit: I think this can overflow.
> >
> > To prevent overflow, I will change it to:
> > 	if (offset > msglen || offset + count * sizeof(u32) > msglen) {
> > Thanks,
> > - Haiyang
> 
> Actually, this would be simpler since we already trust msglen and count
> to have good values:
> 
> 	if (offset > msglen - count * sizeof(u32)) {

Great idea. Thanks!