[PATCH] [v3] ieee802154: ca8210: Fix a potential UAF in ca8210_probe

[Dinghao Liu <dinghao.liu@zju.edu.cn>]

If of_clk_add_provider() fails in ca8210_register_ext_clock(),
it calls clk_unregister() to release priv->clk and returns an
error. However, the caller ca8210_probe() then calls ca8210_remove(),
where priv->clk is freed again in ca8210_unregister_ext_clock(). In
this case, a use-after-free may happen in the second time we call
clk_unregister().

Fix this by removing the first clk_unregister(). Also, priv->clk could
be an error code on failure of clk_register_fixed_rate(). Use
IS_ERR_OR_NULL to catch this case in ca8210_unregister_ext_clock().

Fixes: ded845a781a5 ("ieee802154: Add CA8210 IEEE 802.15.4 device driver")
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---

Changelog:

v2: -Remove the first clk_unregister() instead of nulling priv->clk.

v3: -Simplify ca8210_register_ext_clock().
    -Add a ';' after return in ca8210_unregister_ext_clock().
---
 drivers/net/ieee802154/ca8210.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ieee802154/ca8210.c b/drivers/net/ieee802154/ca8210.c
index aebb19f1b3a4..ae44a9133937 100644
--- a/drivers/net/ieee802154/ca8210.c
+++ b/drivers/net/ieee802154/ca8210.c
@@ -2757,18 +2757,8 @@ static int ca8210_register_ext_clock(struct spi_device *spi)
 		dev_crit(&spi->dev, "Failed to register external clk\n");
 		return PTR_ERR(priv->clk);
 	}
-	ret = of_clk_add_provider(np, of_clk_src_simple_get, priv->clk);
-	if (ret) {
-		clk_unregister(priv->clk);
-		dev_crit(
-			&spi->dev,
-			"Failed to register external clock as clock provider\n"
-		);
-	} else {
-		dev_info(&spi->dev, "External clock set as clock provider\n");
-	}
 
-	return ret;
+	return of_clk_add_provider(np, of_clk_src_simple_get, priv->clk);
 }
 
 /**
@@ -2780,8 +2770,8 @@ static void ca8210_unregister_ext_clock(struct spi_device *spi)
 {
 	struct ca8210_priv *priv = spi_get_drvdata(spi);
 
-	if (!priv->clk)
-		return
+	if (IS_ERR_OR_NULL(priv->clk))
+		return;
 
 	of_clk_del_provider(spi->dev.of_node);
 	clk_unregister(priv->clk);
-- 
2.17.1