[PATCH 1/2] staging: octeon: fix use-after-free in tasklet teardown

[Ayush Mukkanwar <ayushmukkanwar@gmail.com>]

cvm_oct_tx_shutdown() kills the tx cleanup tasklet while
the net devices are still registered. This could lead
to use-after-free when a tasklet is scheduled after the
tasklet_kill() is called which might run after the net
devices are freed.
Fix it by unregistering the net devices before the tasklet
is killed.

Fixes: 4898c560103f ("Staging: Octeon:  Free transmit SKBs in a timely manner")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/message/20260615172734.42038-1-ayushmukkanwar%40gmail.com
Signed-off-by: Ayush Mukkanwar <ayushmukkanwar@gmail.com>
---
Note: This patch has only been compile tested. No runtime testing was
performed as I do not have access to Octeon hardware.

 drivers/staging/octeon/ethernet.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/octeon/ethernet.c b/drivers/staging/octeon/ethernet.c
index 42ec4b8324a8..98d4e025c301 100644
--- a/drivers/staging/octeon/ethernet.c
+++ b/drivers/staging/octeon/ethernet.c
@@ -113,7 +113,6 @@ static void cvm_oct_remove_device(int port)
 		cancel_delayed_work_sync(&priv->port_periodic_work);
 
 		cvm_oct_tx_shutdown_dev(dev);
-		unregister_netdev(dev);
 		free_netdev(dev);
 		cvm_oct_device[port] = NULL;
 	}
@@ -694,6 +693,7 @@ static int cvm_oct_probe(struct platform_device *pdev)
 	struct device_node *pip;
 	int mtu_overhead = ETH_HLEN + ETH_FCS_LEN;
 	struct octeon_ethernet_platform *plat;
+	int port;
 
 	plat = devm_kzalloc(&pdev->dev, sizeof(*plat), GFP_KERNEL);
 	if (!plat)
@@ -729,7 +729,6 @@ static int cvm_oct_probe(struct platform_device *pdev)
 	num_interfaces = cvmx_helper_get_number_of_interfaces();
 	for (interface = 0; interface < num_interfaces; interface++) {
 		int num_ports = cvmx_helper_ports_on_interface(interface);
-		int port;
 
 		for (port = cvmx_helper_get_ipd_port(interface, 0);
 		     port < cvmx_helper_get_ipd_port(interface, num_ports);
@@ -953,8 +952,21 @@ static int cvm_oct_probe(struct platform_device *pdev)
 	return 0;
 
 err_rx:
+	/* Unregister ethernet devices */
+	for (port = 0; port < TOTAL_NUMBER_OF_PORTS; port++)
+		if (cvm_oct_device[port])
+			unregister_netdev(cvm_oct_device[port]);
+
 	cvm_oct_tx_shutdown();
+	goto disable_ipd;
+
 err_tx:
+	/* Unregister ethernet devices */
+	for (port = 0; port < TOTAL_NUMBER_OF_PORTS; port++)
+		if (cvm_oct_device[port])
+			unregister_netdev(cvm_oct_device[port]);
+
+disable_ipd:
 	cvmx_ipd_disable();
 
 	atomic_inc_return(&cvm_oct_poll_queue_stopping);
@@ -984,6 +996,11 @@ static void cvm_oct_remove(struct platform_device *pdev)
 	struct octeon_ethernet_platform *plat = platform_get_drvdata(pdev);
 	int port;
 
+	/* Unregister ethernet devices */
+	for (port = 0; port < TOTAL_NUMBER_OF_PORTS; port++)
+		if (cvm_oct_device[port])
+			unregister_netdev(cvm_oct_device[port]);
+
 	cvmx_ipd_disable();
 
 	atomic_inc_return(&cvm_oct_poll_queue_stopping);
-- 
2.54.0