net: airoha: Move ndesc initialization at end of airoha_qdma_init_rx_queue()

If queue entry or DMA descriptor list allocation fails in
airoha_qdma_init_rx_queue routine, airoha_qdma_cleanup() will trigger a
NULL pointer dereference running netif_napi_del() for RX queue NAPIs
since netif_napi_add() has never been executed to this particular RX NAPI.
The issue is due to the early ndesc initialization in
airoha_qdma_init_rx_queue() since airoha_qdma_cleanup() relies on ndesc
value to check if the queue is properly initialized. Fix the issue moving
ndesc initialization at end of airoha_qdma_init_tx routine.
Move page_pool allocation after descriptor list allocation in order to
avoid memory leaks if desc allocation fails.

Fixes: 23020f0 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260420-airoha_qdma_init_rx_queue-fix-v2-1-d99347e5c18d@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: LorenzoBianconi

drivers/net/ethernet/airoha/airoha_eth.c

@@ -745,14 +745,18 @@ static int airoha_qdma_init_rx_queue(struct airoha_queue *q,
 	dma_addr_t dma_addr;
 
 	q->buf_size = PAGE_SIZE / 2;
-	q->ndesc = ndesc;
 	q->qdma = qdma;
 
-	q->entry = devm_kzalloc(eth->dev, q->ndesc * sizeof(*q->entry),
+	q->entry = devm_kzalloc(eth->dev, ndesc * sizeof(*q->entry),
 				GFP_KERNEL);
 	if (!q->entry)
 		return -ENOMEM;
 
+	q->desc = dmam_alloc_coherent(eth->dev, ndesc * sizeof(*q->desc),
+				      &dma_addr, GFP_KERNEL);
+	if (!q->desc)
+		return -ENOMEM;
+
 	q->page_pool = page_pool_create(&pp_params);
 	if (IS_ERR(q->page_pool)) {
 		int err = PTR_ERR(q->page_pool);
@@ -761,11 +765,7 @@ static int airoha_qdma_init_rx_queue(struct airoha_queue *q,
 		return err;
 	}
 
-	q->desc = dmam_alloc_coherent(eth->dev, q->ndesc * sizeof(*q->desc),
-				      &dma_addr, GFP_KERNEL);
-	if (!q->desc)
-		return -ENOMEM;
-
+	q->ndesc = ndesc;
 	netif_napi_add(eth->napi_dev, &q->napi, airoha_qdma_rx_napi_poll);
 
 	airoha_qdma_wr(qdma, REG_RX_RING_BASE(qid), dma_addr);