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

[Dinghao Liu]

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 nulling priv->clk after the first clk_unregister(). Also
refine the pointer checking in ca8210_unregister_ext_clock().

Fixes: ded845a781a5 ("ieee802154: Add CA8210 IEEE 802.15.4 device driver")
Signed-off-by: Dinghao Liu <dinghao....@zju.edu.cn>
---
 drivers/net/ieee802154/ca8210.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ieee802154/ca8210.c b/drivers/net/ieee802154/ca8210.c
index aebb19f1b3a4..1d545879c000 100644
--- a/drivers/net/ieee802154/ca8210.c
+++ b/drivers/net/ieee802154/ca8210.c
@@ -2760,6 +2760,7 @@ static int ca8210_register_ext_clock(struct spi_device 
*spi)
        ret = of_clk_add_provider(np, of_clk_src_simple_get, priv->clk);
        if (ret) {
                clk_unregister(priv->clk);
+               priv->clk = NULL;
                dev_crit(
                        &spi->dev,
                        "Failed to register external clock as clock provider\n"
@@ -2780,7 +2781,7 @@ static void ca8210_unregister_ext_clock(struct spi_device 
*spi)
 {
        struct ca8210_priv *priv = spi_get_drvdata(spi);
 
-       if (!priv->clk)
+       if (IS_ERR_OR_NULL(priv->clk))
                return
 
        of_clk_del_provider(spi->dev.of_node);
-- 
2.17.1