ice: Add a boundary check in ice_xsk_umem()

In ice_xsk_umem(), variable qid which is later used as an array index,
is not validated for a possible boundary exceedance. Because of that,
a calling function might receive an invalid address, which causes
general protection fault when dereferenced.

To address this, add a boundary check to see if qid is greater than the
size of a UMEM array. Also, don't let user change vsi->num_xsk_umems
just by trying to setup a second UMEM if its value is already set up
(i.e. UMEM region has already been allocated for this VSI).

While at it, make sure that ring->zca.free pointer is always zeroed out
if there is no UMEM on a specified ring.
Signed-off-by: Krzysztof Kazimierczak <krzysztof.kazimierczak@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ice/ice.h

@@ -465,12 +465,13 @@ static inline void ice_set_ring_xdp(struct ice_ring *ring)
 static inline struct xdp_umem *ice_xsk_umem(struct ice_ring *ring)
 {
 	struct xdp_umem **umems = ring->vsi->xsk_umems;
-	int qid = ring->q_index;
+	u16 qid = ring->q_index;
 
 	if (ice_ring_is_xdp(ring))
 		qid -= ring->vsi->num_xdp_txq;
 
-	if (!umems || !umems[qid] || !ice_is_xdp_ena_vsi(ring->vsi))
+	if (qid >= ring->vsi->num_xsk_umems || !umems || !umems[qid] ||
+	    !ice_is_xdp_ena_vsi(ring->vsi))
 		return NULL;
 
 	return umems[qid];

drivers/net/ethernet/intel/ice/ice_base.c

@@ -326,6 +326,7 @@ int ice_setup_rx_ctx(struct ice_ring *ring)
 			dev_info(&vsi->back->pdev->dev, "Registered XDP mem model MEM_TYPE_ZERO_COPY on Rx ring %d\n",
 				 ring->q_index);
 		} else {
+			ring->zca.free = NULL;
 			if (!xdp_rxq_info_is_reg(&ring->xdp_rxq))
 				xdp_rxq_info_reg(&ring->xdp_rxq,
 						 ring->netdev,

drivers/net/ethernet/intel/ice/ice_xsk.c

@@ -414,6 +414,7 @@ ice_xsk_umem_enable(struct ice_vsi *vsi, struct xdp_umem *umem, u16 qid)
 	if (vsi->type != ICE_VSI_PF)
 		return -EINVAL;
 
+	if (!vsi->num_xsk_umems)
 		vsi->num_xsk_umems = min_t(u16, vsi->num_rxq, vsi->num_txq);
 	if (qid >= vsi->num_xsk_umems)
 		return -EINVAL;