[PATCH v1] net: atlantic: Unregister before clearing RXNFC rules

[Binbin Deng]

aq_pci_remove() clears the driver's RXNFC rule list before unregistering
the netdevice.  Until unregister_netdev() returns, ethtool operations can
still call aq_get_rxnfc_rule(), aq_get_rxnfc_all_rules(),
aq_add_rxnfc_rule(), or aq_del_rxnfc_rule().  Those paths traverse the
same unlocked hlist that aq_clear_rxnfc_all_rules() is mutating and
freeing.

The race is reachable by issuing RXNFC ethtool commands concurrently with
PCI device removal or driver unbind.  A reader can dereference a node that
has just been freed, and two writers can corrupt the list or free the same
rule more than once, causing KASAN reports, list corruption, or a kernel
panic.

Reverse the removal order: unregister the netdevice first, then clear the
RXNFC rules.  After unregister_netdev() returns, ethtool can no longer
enter the driver, while the PCI device is still available for the
rule-clearing routine to issue hardware commands.

Found during a static-analysis-assisted audit: candidate sites were
surfaced by a Coccinelle rule, and the reader/writer paths were
confirmed by LLM-assisted (GLM-5.3) code inspection.  The issue was
not observed at runtime; it is identified by code inspection only.

Fixes: 8d0bcb012f57 ("net: aquantia: add infrastructure for ntuple rules")
Assisted-by: GLM-5.3 coccinelle
Signed-off-by: Binbin Deng <18983559317@xxxxxxx>
---
 drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c b/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c
index 005d6ef4fc36..881727c3aa0a 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c
@@ -344,9 +344,9 @@ static void aq_pci_remove(struct pci_dev *pdev)
 	struct aq_nic_s *self = pci_get_drvdata(pdev);
 
 	if (self->ndev) {
-		aq_clear_rxnfc_all_rules(self);
 		if (self->ndev->reg_state == NETREG_REGISTERED)
 			unregister_netdev(self->ndev);
+		aq_clear_rxnfc_all_rules(self);
 
 #if IS_ENABLED(CONFIG_MACSEC)
 		aq_macsec_free(self);
-- 
2.43.0