[PATCH v2] HSI: ssi_protocol: Fix use after free vulnerability in ssi_protocol Driver Due to Race Condition

[PATCH v2] HSI: ssi_protocol: Fix use after free vulnerability in ssi_protocol Driver Due to Race Condition

[Kaixin Wang]

In the ssi_protocol_probe function, &ssi->work is bound with
ssip_xmit_work, In ssip_pn_setup, the ssip_pn_xmit function
within the ssip_pn_ops structure is capable of starting the
work.

If we remove the module which will call ssi_protocol_remove
to make a cleanup, it will free ssi through kfree(ssi),
while the work mentioned above will be used. The sequence
of operations that may lead to a UAF bug is as follows:

CPU0                                    CPU1

                        | ssip_xmit_work
ssi_protocol_remove     |
kfree(ssi);             |
                        | struct hsi_client *cl = ssi->cl;
                        | // use ssi

Fix it by ensuring that the work is canceled before proceeding
with the cleanup in ssi_protocol_remove.

Signed-off-by: Kaixin Wang <kxwang23@m.fudan.edu.cn>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

---
v2:
- cancel the work in ssip_reset(), suggested by Sebastian
- add the Acked-by label from Andy
- Link to v1: https://lore.kernel.org/r/20240911151915.844957-1-kxwang23@m.fudan.edu.cn
---
 drivers/hsi/clients/ssi_protocol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hsi/clients/ssi_protocol.c b/drivers/hsi/clients/ssi_protocol.c
index afe470f3661c..6105ea9a6c6a 100644
--- a/drivers/hsi/clients/ssi_protocol.c
+++ b/drivers/hsi/clients/ssi_protocol.c
@@ -401,6 +401,7 @@ static void ssip_reset(struct hsi_client *cl)
 	del_timer(&ssi->rx_wd);
 	del_timer(&ssi->tx_wd);
 	del_timer(&ssi->keep_alive);
+	cancel_work_sync(&ssi->work);
 	ssi->main_state = 0;
 	ssi->send_state = 0;
 	ssi->recv_state = 0;
-- 
2.39.1.windows.1

Re: [PATCH v2] HSI: ssi_protocol: Fix use after free vulnerability in ssi_protocol Driver Due to Race Condition

[Andy Shevchenko]

On Sun, Sep 15, 2024 at 01:21:43AM +0800, Kaixin Wang wrote:
> In the ssi_protocol_probe function, &ssi->work is bound with
> ssip_xmit_work, In ssip_pn_setup, the ssip_pn_xmit function
> within the ssip_pn_ops structure is capable of starting the
> work.

We refer to the functions as func(). E.g., ssip_pn_setup(),
ssip_pn_xmit().

> If we remove the module which will call ssi_protocol_remove
> to make a cleanup, it will free ssi through kfree(ssi),
> while the work mentioned above will be used. The sequence
> of operations that may lead to a UAF bug is as follows:
> 
> CPU0                                    CPU1
> 
>                         | ssip_xmit_work
> ssi_protocol_remove     |
> kfree(ssi);             |
>                         | struct hsi_client *cl = ssi->cl;
>                         | // use ssi
> 
> Fix it by ensuring that the work is canceled before proceeding
> with the cleanup in ssi_protocol_remove.

Same here.

...

> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> - add the Acked-by label from Andy

Not that Ack was given to _this_ version of the change (it has been changed
a lot), but I'm fine with keeping it.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] HSI: ssi_protocol: Fix use after free vulnerability in ssi_protocol Driver Due to Race Condition

[Kaixin Wang]

At 2024-09-16 18:39:46, "Andy Shevchenko" <andriy.shevchenko@linux.intel.com> wrote:
>On Sun, Sep 15, 2024 at 01:21:43AM +0800, Kaixin Wang wrote:
>> In the ssi_protocol_probe function, &ssi->work is bound with
>> ssip_xmit_work, In ssip_pn_setup, the ssip_pn_xmit function
>> within the ssip_pn_ops structure is capable of starting the
>> work.
>
>We refer to the functions as func(). E.g., ssip_pn_setup(),
>ssip_pn_xmit().
>

I will correct it.

>> If we remove the module which will call ssi_protocol_remove
>> to make a cleanup, it will free ssi through kfree(ssi),
>> while the work mentioned above will be used. The sequence
>> of operations that may lead to a UAF bug is as follows:
>> 
>> CPU0                                    CPU1
>> 
>>                         | ssip_xmit_work
>> ssi_protocol_remove     |
>> kfree(ssi);             |
>>                         | struct hsi_client *cl = ssi->cl;
>>                         | // use ssi
>> 
>> Fix it by ensuring that the work is canceled before proceeding
>> with the cleanup in ssi_protocol_remove.
>
>Same here.
>

I will correct it.

>...
>
>> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>
>> - add the Acked-by label from Andy
>
>Not that Ack was given to _this_ version of the change (it has been changed
>a lot), but I'm fine with keeping it.
>

Sorry, I missed this point.

>-- 
>With Best Regards,
>Andy Shevchenko
>
>
>

Best regards,
Kaixin Wang