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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rosen Penev , linux-kernel@vger.kernel.org (open list) Subject: [PATCH net] net: ibm: emac: Fix use-after-free during device removal Date: Wed, 3 Jun 2026 15:12:17 -0700 Message-ID: <20260603221217.55592-1-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The driver was using devm_register_netdev() which causes unregister_netdev() to be deferred until the devres cleanup phase, which runs after emac_remove() returns. This creates a use-after-free window where: 1. emac_remove() is called, which tears down hardware (cancels work, detaches modules, unregisters from MAL) 2. emac_remove() returns 3. devres cleanup runs and finally calls unregister_netdev() During step 3, the network stack might still process packets, triggering emac_irq(), emac_poll(), or other handlers that access now-freed hardware resources (dev->emacp, dev->mal, etc.). Fix this by replacing devm_register_netdev() with manual register_netdev() and calling unregister_netdev() at the beginning of emac_remove(), before any hardware teardown. This ensures the network device is fully stopped and unregistered before hardware resources are released. The change is safe because: - dev->ndev is assigned very early in probe (before any error paths that could bypass emac_remove) - platform_set_drvdata() is only called after successful registration, so emac_remove() only runs for fully registered devices - unregister_netdev() is idempotent and safe to call on any registered device Fixes: a4dd8535a527 ("net: ibm: emac: use devm for register_netdev") Assisted-by: opencode:big-pickle Signed-off-by: Rosen Penev --- drivers/net/ethernet/ibm/emac/core.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c index d9bbcfbcf60e..00a36c839d82 100644 --- a/drivers/net/ethernet/ibm/emac/core.c +++ b/drivers/net/ethernet/ibm/emac/core.c @@ -3151,7 +3151,7 @@ static int emac_probe(struct platform_device *ofdev) netif_carrier_off(ndev); - err = devm_register_netdev(&ofdev->dev, ndev); + err = register_netdev(ndev); if (err) { printk(KERN_ERR "%pOF: failed to register net device (%d)!\n", np, err); @@ -3204,6 +3204,13 @@ static void emac_remove(struct platform_device *ofdev) DBG(dev, "remove" NL); + /* Unregister network device before tearing down hardware + * to prevent use-after-free during deferred cleanup. This ensures + * the network stack stops all operations before hardware resources + * are released. + */ + unregister_netdev(dev->ndev); + cancel_work_sync(&dev->reset_work); if (emac_has_feature(dev, EMAC_FTR_HAS_TAH)) -- 2.54.0