[PATCH] media: cx23885: unregister DVB bus when SP2 CI setup fails

[Myeonghun Pak <mhun512@gmail.com>]

The DVBSKY S950C, DVBSKY T980C and TechnoTrend CT2-4500 CI paths register
the DVB bus before attaching their SP2 CI client. If that client cannot be
created, bound, or pinned, the current error path removes the I2C frontend
components and only deallocates the frontend list, leaving the registered
DVB adapter behind. Removing an I2C demod before unregistering the DVB bus
can also expose the use-after-free ordering fixed for the normal remove
path.

Unregister the DVB bus immediately when SP2 CI setup fails, before the
existing I2C client cleanup. The bus helper empties the frontend list, so
the later frontend deallocation has nothing left to release. Keep failures
from vb2_dvb_register_bus() on the existing cleanup path. Also release an
unbound SP2 client and propagate the actual I2C creation or CI registration
error.

This issue was identified during our ongoing static-analysis research while
reviewing kernel code.

Fixes: 2b0aac3011bc ("[media] cx23885: move CI/MAC registration to a separate function")
Cc: stable@vger.kernel.org
Assisted-by: OpenAI:GPT-5.6
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
---
 drivers/media/pci/cx23885/cx23885-dvb.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/media/pci/cx23885/cx23885-dvb.c b/drivers/media/pci/cx23885/cx23885-dvb.c
--- a/drivers/media/pci/cx23885/cx23885-dvb.c
+++ b/drivers/media/pci/cx23885/cx23885-dvb.c
@@ -1158,8 +1158,12 @@ static int dvb_register_ci_mac(struct cx23885_tsport *port)
 		info.platform_data = &sp2_config;
 		request_module(info.type);
 		client_ci = i2c_new_client_device(&i2c_bus->i2c_adap, &info);
-		if (!i2c_client_has_driver(client_ci))
+		if (IS_ERR(client_ci))
+			return PTR_ERR(client_ci);
+		if (!client_ci->dev.driver) {
+			i2c_unregister_device(client_ci);
 			return -ENODEV;
+		}
 		if (!try_module_get(client_ci->dev.driver->owner)) {
 			i2c_unregister_device(client_ci);
 			return -ENODEV;
@@ -1202,7 +1206,7 @@ static int dvb_register(struct cx23885_tsport *port)
 	int (*p_set_voltage)(struct dvb_frontend *fe,
 			     enum fe_sec_voltage voltage) = NULL;
 	int mfe_shared = 0; /* bus not shared by default */
-	int ret;
+	int ret = -EINVAL;
 
 	/* Get the first frontend */
 	fe0 = vb2_dvb_get_frontend(&port->frontends, 1);
@@ -2587,8 +2591,10 @@ static int dvb_register(struct cx23885_tsport *port)
 
 	ret = dvb_register_ci_mac(port);
-	if (ret)
+	if (ret) {
+		vb2_dvb_unregister_bus(&port->frontends);
 		goto frontend_detach;
+	}
 
 	return 0;
 
 frontend_detach:
@@ -2618,7 +2624,7 @@ static int dvb_register(struct cx23885_tsport *port)
 
 	port->gate_ctrl = NULL;
 	vb2_dvb_dealloc_frontends(&port->frontends);
-	return -EINVAL;
+	return ret;
 }
 
 int cx23885_dvb_register(struct cx23885_tsport *port)
-- 
2.47.1