net: sparx5: switchdev: fix possible NULL pointer dereference

As the possible failure of the allocation, devm_kzalloc() may return NULL
pointer.
Therefore, it should be better to check the 'db' in order to prevent
the dereference of NULL pointer.

Fixes: 1061590 ("net: sparx5: switchdev: adding frame DMA functionality")
Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/sparx5/sparx5_fdma.c

@@ -422,6 +422,8 @@ static int sparx5_fdma_tx_alloc(struct sparx5 *sparx5)
 			db_hw->dataptr = phys;
 			db_hw->status = 0;
 			db = devm_kzalloc(sparx5->dev, sizeof(*db), GFP_KERNEL);
+			if (!db)
+				return -ENOMEM;
 			db->cpu_addr = cpu_addr;
 			list_add_tail(&db->list, &tx->db_list);
 		}