macb: Don't unregister clks unconditionally

The only clk init function in this driver that register a clk is
fu540_c000_clk_init(), and thus we need to unregister the clk when this
driver is removed on that platform. Other init functions, for example
macb_clk_init(), don't register clks and therefore we shouldn't
unregister the clks when this driver is removed. Convert this
registration path to devm so it gets auto-unregistered when this driver
is removed and drop the clk_unregister() calls in driver remove (and
error paths) so that we don't erroneously remove a clk from the system
that isn't registered by this driver.

Otherwise we get strange crashes with a use-after-free when the
devm_clk_get() call in macb_clk_init() calls clk_put() on a clk pointer
that has become invalid because it is freed in clk_unregister().

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Yash Shah <yash.shah@sifive.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: c218ad55 ("macb: Add support for SiFive FU540-C000")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -4088,7 +4088,7 @@ static int fu540_c000_clk_init(struct platform_device *pdev, struct clk **pclk,
 	mgmt->rate = 0;
 	mgmt->hw.init = &init;
 
-	*tx_clk = clk_register(NULL, &mgmt->hw);
+	*tx_clk = devm_clk_register(&pdev->dev, &mgmt->hw);
 	if (IS_ERR(*tx_clk))
 		return PTR_ERR(*tx_clk);
 
@@ -4416,7 +4416,6 @@ static int macb_probe(struct platform_device *pdev)
 
 err_disable_clocks:
 	clk_disable_unprepare(tx_clk);
-	clk_unregister(tx_clk);
 	clk_disable_unprepare(hclk);
 	clk_disable_unprepare(pclk);
 	clk_disable_unprepare(rx_clk);
@@ -4446,7 +4445,6 @@ static int macb_remove(struct platform_device *pdev)
 		pm_runtime_dont_use_autosuspend(&pdev->dev);
 		if (!pm_runtime_suspended(&pdev->dev)) {
 			clk_disable_unprepare(bp->tx_clk);
-			clk_unregister(bp->tx_clk);
 			clk_disable_unprepare(bp->hclk);
 			clk_disable_unprepare(bp->pclk);
 			clk_disable_unprepare(bp->rx_clk);