[PATCH] net: tn40xx: fix netdev and NAPI leak in probe error paths

[ZhaoJinming <zhaojinming@uniontech.com>]

In tn40_probe(), after tn40_netdev_alloc() and netif_napi_add() succeed,
none of the subsequent error paths call netif_napi_del() or free_netdev()
to undo these operations.  On any probe failure after netif_napi_add() the
NAPI structure (embedded in the netdev private data) remains on the
per-netdev napi_list while the backing memory is never freed, causing:

  - A permanent memory leak of the net_device and its private data
    (includes DMA rings, descriptor arrays and other internal structures
    allocated by tn40_priv_init).
  - A stale napi_list node that references already-freed memory, which
    is a use-after-free if the list is traversed after probe failure.

Fix by renaming err_unset_drvdata to err_free_netdev, adding
netif_napi_del() and free_netdev() calls there, and redirecting the
tn40_hw_reset() and pci_alloc_irq_vectors() failure paths to this new
label so that all error paths after netdev allocation properly release
the netdev and NAPI resources.

Fixes: dd2a0ff55408 ("net: tn40xx: add basic Tx handling")
Signed-off-by: ZhaoJinming <zhaojinming@uniontech.com>
---
 drivers/net/ethernet/tehuti/tn40.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/tehuti/tn40.c b/drivers/net/ethernet/tehuti/tn40.c
index 558b791a97ed..532703e9c28e 100644
--- a/drivers/net/ethernet/tehuti/tn40.c
+++ b/drivers/net/ethernet/tehuti/tn40.c
@@ -1751,13 +1751,13 @@ static int tn40_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	ret = tn40_hw_reset(priv);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to reset HW.\n");
-		goto err_unset_drvdata;
+		goto err_free_netdev;
 	}
 
 	ret = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_MSI);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to allocate irq.\n");
-		goto err_unset_drvdata;
+		goto err_free_netdev;
 	}
 
 	ret = tn40_mdiobus_init(priv);
@@ -1799,8 +1799,10 @@ static int tn40_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	tn40_swnodes_cleanup(priv);
 err_free_irq:
 	pci_free_irq_vectors(pdev);
-err_unset_drvdata:
+err_free_netdev:
+	netif_napi_del(&priv->napi);
 	pci_set_drvdata(pdev, NULL);
+	free_netdev(ndev);
 err_iounmap:
 	iounmap(regs);
 err_free_regions:
-- 
2.20.1