[PATCH] macb: Don't unregister clks unconditionally

Stephen Boyd
2020-01-04T00:19:24Z

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: c218ad559020 ("macb: Add support for SiFive FU540-C000")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
---
drivers/net/ethernet/cadence/macb_main.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 9c767ee252ac..7dce403fd27c 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -4069,7 +4069,7 @@ 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);

@@ -4397,7 +4397,6 @@ 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);
@@ -4427,7 +4426,6 @@ 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);
--
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