i40e: validate VSI param from VFs

Validate that the VF has sent us a valid VSI index before actually using
that index. Without this code, a malicious or buggy VF driver could
panic the host by sending an invalid index into the VSI array.

Change-ID: I66a177687a0dcc281ec83e714d3813d70d18c8b4
Reported-by: NNick Nunley <nicholas.d.nunley@intel.com>
Signed-off-by: NMitch Williams <mitch.a.williams@intel.com>
Tested-by: NJim Young <james.m.young@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c

@@ -57,6 +57,8 @@ static inline bool i40e_vc_isvalid_vsi_id(struct i40e_vf *vf, u8 vsi_id)
 {
 	struct i40e_pf *pf = vf->pf;
 
+	if (vsi_id > pf->num_alloc_vsi)
+		return false;
 	return pf->vsi[vsi_id]->vf_id == vf->vf_id;
 }