[PATCH net] e1000e: roll back registered MSI-X IRQs on failure

[Runyu Xiao <runyu.xiao@seu.edu.cn>]

e1000_request_msix() requests the RX, TX, and other-cause interrupt
handlers sequentially. If a later request_irq() fails, the function
returns without releasing handlers that were registered earlier. The
caller then disables MSI-X and falls back to MSI or legacy interrupts,
leaving those handlers registered against disabled MSI-X vectors.

Free all handlers registered before the failing request in reverse order
before returning the error. The failed vector is not freed, and the
existing fallback path can then disable MSI-X without retaining stale
handlers.

A QEMU e1000e test with deterministic failure injection at the third
request_irq() reproduced a residual IRQ entry and warning on the
unfixed kernel. The fixed kernel reached the same fallback without the
residual entry. The injection is deliberate and does not claim that a
third request_irq() failure occurs spontaneously during normal operation.

Fixes: 4662e82b2cb4 ("e1000e: add support for new 82574L part")
Cc: stable@vger.kernel.org
Assisted-by: LLM Codex
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 844f31ab37ad4..f55aec340342b 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -2139,7 +2139,7 @@ static int e1000_request_msix(struct e1000_adapter *adapter)
 			  e1000_intr_msix_tx, 0, adapter->tx_ring->name,
 			  netdev);
 	if (err)
-		return err;
+		goto err_irq;
 	adapter->tx_ring->itr_register = adapter->hw.hw_addr +
 	    E1000_EITR_82574(vector);
 	adapter->tx_ring->itr_val = adapter->itr;
@@ -2148,11 +2148,16 @@ static int e1000_request_msix(struct e1000_adapter *adapter)
 	err = request_irq(adapter->msix_entries[vector].vector,
 			  e1000_msix_other, 0, netdev->name, netdev);
 	if (err)
-		return err;
+		goto err_irq;
 
 	e1000_configure_msix(adapter);
 
 	return 0;
+
+err_irq:
+	while (vector)
+		free_irq(adapter->msix_entries[--vector].vector, netdev);
+	return err;
 }
 
 /**
-- 
2.34.1