2023-09-25 07:35:15

by Dinghao Liu

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

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 <[email protected]>
---
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

2023-09-25 09:06:37

by Dinghao Liu

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

Hi Miquèl,

> > 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;
>
> This function is a bit convoluted. You could just return the result of
> of_clk_add_provider() (keep the printk's if you want, they don't seem
> very useful) and let ca8210_unregister_ext_clock() do the cleanup.

Thanks for your advice! I will resend a new patch as suggested.

>
> > 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))
>
> Does not look useful as you are enforcing priv->clock to be valid or
> NULL, it cannot be an error code.

I find that ca8210_register_ext_clock() uses IS_ERR to check priv->clk
after calling clk_register_fixed_rate(). So I think priv->clk could be
a non-null pointer even on failure. And a null pointer check may miss
this case in ca8210_unregister_ext_clock().

Regards,
Dinghao

2023-09-25 15:19:27

by Miquel Raynal

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

Hi Dinghao,

[email protected] wrote on Mon, 25 Sep 2023 15:24:22 +0800:

> 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 <[email protected]>
> ---
> 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;

This function is a bit convoluted. You could just return the result of
of_clk_add_provider() (keep the printk's if you want, they don't seem
very useful) and let ca8210_unregister_ext_clock() do the cleanup.

> 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))

Does not look useful as you are enforcing priv->clock to be valid or
NULL, it cannot be an error code.

Thanks,
Miquèl