linux-kernel - [PATCH v2] HSI: ssi_protocol: Fix use after free vulnerability in ssi

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Message-Id: <20240914172142.328-1-kxwang23@m.fudan.edu.cn>
Date: Sun, 15 Sep 2024 01:21:43 +0800
From: Kaixin Wang <kxwang23@...udan.edu.cn>
To: sre@...nel.org
Cc: andriy.shevchenko@...ux.intel.com,
	rdunlap@...radead.org,
	linux-kernel@...r.kernel.org,
	21210240012@...udan.edu.cn,
	21302010073@...udan.edu.cn,
	Kaixin Wang <kxwang23@...udan.edu.cn>
Subject: [PATCH v2] HSI: ssi_protocol: Fix use after free vulnerability in ssi_protocol Driver Due to Race Condition

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@...udan.edu.cn>
Acked-by: Andy Shevchenko <andriy.shevchenko@...ux.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