[PATCH] 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@xxxxxxxxxxxxxx>
---
 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..3506c70e3505 100644
--- a/drivers/hsi/clients/ssi_protocol.c
+++ b/drivers/hsi/clients/ssi_protocol.c
@@ -1155,6 +1155,7 @@ static int ssi_protocol_remove(struct device *dev)
 	unregister_netdev(ssi->netdev);
 	ssip_free_cmds(ssi);
 	hsi_client_set_drvdata(cl, NULL);
+	cancel_work_sync(&ssi->work)
 	kfree(ssi);
 
 	return 0;
-- 
2.25.1