[PATCH v3] HSI: ssi_protocol: Fix use after free vulnerability in ssi_protocol Driver Due to Race Condition

Kaixin Wang
2024-09-18T12:09:40Z

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>

---
v3:
- refer to the functions in the form of func() in the description message.
- Link to v2: https://lore.kernel.org/r/20240914172142.328-1-kxwang23@m.fudan.edu.cn
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