[PATCH net v5] net: e1000: fix warning in iounmap on probe failure

In e1000_probe(), the error unwinding path at err_sw_init unconditionally
calls iounmap(hw->ce4100_gbe_mdio_base_virt). On non-CE4100 hardware,
hw->ce4100_gbe_mdio_base_virt remains NULL.
Passing NULL to iounmap() triggers a WARN_ON_ONCE on x86 architectures.
Furthermore, on CE4100 hardware, if probe fails before or during
MDIO mapping, ce4100_gbe_mdio_base_virt is also NULL.

Fix this by adding a NULL pointer check before calling iounmap() on
hw->ce4100_gbe_mdio_base_virt. iounmap(hw->hw_addr) remains unconditional
because every code path reaching err_sw_init occurs after hw->hw_addr has
been successfully mapped.

Reported-by: syzbot+ca1ef9e2e234b8d3599b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ca1ef9e2e234b8d3599b
Fixes: 13acde8fffc0 ("e1000: cleanup CE4100 MDIO registers access")
Cc: stable@vger.kernel.org
Signed-off-by: Svyatoslav Nikolenko <redacted>
---
v5:
  - Updated commit message and changelog to accurately describe the NULL pointer
    check implemented in the diff.
  - Fixed subject string in the Fixes: tag to match commit 13acde8fffc0.
v4:
  - Actually include the code changes (v3 was sent un-staged by mistake)
v3:
  - Switched from pointer null-checks to checking hw->mac_type == e1000_ce4100
  - Removed redundant check for hw->hw_addr since it cannot be NULL here
  - Added missing Cc: stable tag and Closes tag
v2:
  - Expanded commit message to answer reviewer questions (reproduction details)
  - Added appropriate Fixes tags

 drivers/net/ethernet/intel/e1000/e1000_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index d7f5c6f16142..d7e279b739b8 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -1227,7 +1227,8 @@ 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);
+	if (hw->ce4100_gbe_mdio_base_virt)
+		iounmap(hw->ce4100_gbe_mdio_base_virt);
 	iounmap(hw->hw_addr);
 err_ioremap:
 	disable_dev = !test_and_set_bit(__E1000_DISABLED, &adapter->flags);

-- 
2.47.3