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

[Haiyang Zhang <haiyangz@microsoft.com>]

> -----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