[PATCH net v4] net: e1000: fix warning in iounmap on probe failure

[Svyatoslav Nikolenko <nsvatoslav515@gmail.com>]

When e1000_probe() fails, the shared error handling ladder attempts to
iounmap() the hw->ce4100_gbe_mdio_base_virt pointer. If the hardware is
not a CE4100, this pointer remains uninitialized (NULL). On architectures
like x86, passing a NULL pointer to iounmap() triggers a WARN_ON_ONCE,
which is fatal under panic_on_warn.

Fix this by conditionally unmapping the CE4100 MDIO base only if the
mac_type is e1000_ce4100, matching the exact logic used in e1000_remove().
The hw->hw_addr iounmap() remains unconditional since it is guaranteed to
be valid for all error paths reaching the err_sw_init label.

Reported-by: syzbot+ca1ef9e2e234b8d3599b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ca1ef9e2e234b8d3599b
Fixes: 13acde8fffc0af ("e1000: Fix the CE4100 bus type for the MDIO/PHY registers")
Cc: stable@vger.kernel.org
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Svyatoslav Nikolenko <nsvatoslav515@gmail.com>
---
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
  - Added Reviewed-by tag from Aleksandr Loktionov

 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