[PATCH net v2] net: e1000: fix warning in iounmap on probe failure

[Svyatoslav Nikolenko <nsvatoslav515@gmail.com>]

During a probe failure, the e1000 driver error handling path calls
iounmap() on hw->ce4100_gbe_mdio_base_virt and hw->hw_addr without
checking if they were previously mapped. This triggers a kernel warning
(WARN) rather than a fatal crash when passed an uninitialized pointer.

This issue was found by Syzbot. The exact kernel configuration (.config)
and the C reproducer used to trigger this warning are available on the
Syzbot dashboard.

Fix this by adding NULL checks before calling iounmap().

Reported-by: syzbot+ca1ef9e2e234b8d3599b@syzkaller.appspotmail.com
Fixes: 13acde8fffc0a ("e1000: cleanup CE4100 MDIO registers access")
Fixes: 1dc329180fe22 ("e1000: Use hw, er32, and ew32")
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Svyatoslav Nikolenko <nsvatoslav515@gmail.com>
---
v2:
  - Expanded commit message to answer reviewer questions (reproduction details)
  - Added appropriate Fixes tags
  - Added Reviewed-by tag from Aleksandr Loktionov

 drivers/net/ethernet/intel/e1000/e1000_main.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index d7f5c6f16142..156903089fa6 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -1227,8 +1227,10 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	kfree(adapter->rx_ring);
 err_dma:
 err_sw_init:
-	iounmap(hw->ce4100_gbe_mdio_base_virt);
-	iounmap(hw->hw_addr);
+	if (hw->ce4100_gbe_mdio_base_virt)
+		iounmap(hw->ce4100_gbe_mdio_base_virt);
+	if (hw->hw_addr)
+		iounmap(hw->hw_addr);
 err_ioremap:
 	disable_dev = !test_and_set_bit(__E1000_DISABLED, &adapter->flags);
 	free_netdev(netdev);
-- 
2.47.3