[PATCH 10/12] [media] dvb_frontend: move kref to struct dvb_frontend
From: Max Kellermann
Date: Tue Aug 09 2016 - 17:44:35 EST
This commit amends my old commit fe35637b0a9f ("[media] dvb_frontend:
eliminate blocking wait in dvb_unregister_frontend()"), which added
kref to struct dvb_frontend_private. It turned out that there are
several use-after-free bugs left, which affect the struct
dvb_frontend. Protecting it with kref also protects struct
dvb_frontend_private, so we can simply move it.
This is how the use-after-free looks like in KASAN:
BUG: KASAN: use-after-free in string+0x60/0xb1 at addr ffff880033bd9fc0
Read of size 1 by task kworker/0:2/617
CPU: 0 PID: 617 Comm: kworker/0:2 Not tainted 4.8.0-rc1-hosting+ #60
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
0000000000000000 ffff880033757218 ffffffff81394e50 ffff880033bd9fd0
ffff880035c03b00 ffff880033757240 ffffffff811f271d ffff880033bd9fc0
1ffff1000677b3f8 ffffed000677b3f8 ffff8800337572b8 ffffffff811f2afe
Call Trace:
[...]
[<ffffffff813a2d2f>] vsnprintf+0x39d/0x7e9
[<ffffffff813993f9>] add_uevent_var+0x10f/0x1dc
[<ffffffff814fe5ca>] rc_dev_uevent+0x55/0x6f
[<ffffffff814438f8>] dev_uevent+0x2e1/0x316
[<ffffffff81399744>] kobject_uevent_env+0x27e/0x701
[<ffffffff81399bd2>] kobject_uevent+0xb/0xd
[<ffffffff81443445>] device_del+0x322/0x383
[<ffffffff81500c0c>] rc_unregister_device+0x98/0xc3
[<ffffffff81508fb4>] dvb_usb_remote_exit+0x7a/0x90
[<ffffffff81506157>] dvb_usb_exit+0x1d/0xe5
[<ffffffff81506e90>] dvb_usb_device_exit+0x69/0x7d
[<ffffffff8150a181>] pctv452e_usb_disconnect+0x7b/0x80
[...]
Object at ffff880033bd9fc0, in cache kmalloc-16 size: 16
Allocated:
[...]
Freed:
PID = 617
[...]
[<ffffffff811f034c>] kfree+0xd9/0x166
[<ffffffff814fe513>] ir_free_table+0x2f/0x51
[<ffffffff81500bc1>] rc_unregister_device+0x4d/0xc3
[<ffffffff81508fb4>] dvb_usb_remote_exit+0x7a/0x90
[<ffffffff81506157>] dvb_usb_exit+0x1d/0xe5
[<ffffffff81506e90>] dvb_usb_device_exit+0x69/0x7d
[<ffffffff8150a181>] pctv452e_usb_disconnect+0x7b/0x80
Another one:
BUG: KASAN: use-after-free in do_sys_poll+0x336/0x6b8 at addr ffff88003563fcc0
Read of size 8 by task tuner on fronte/1042
CPU: 1 PID: 1042 Comm: tuner on fronte Tainted: G B 4.8.0-rc1-hosting+ #60
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
0000000000000000 ffff88003353f910 ffffffff81394e50 ffff88003563fd80
ffff880035c03200 ffff88003353f938 ffffffff811f271d ffff88003563fc80
1ffff10006ac7f98 ffffed0006ac7f98 ffff88003353f9b0 ffffffff811f2afe
Call Trace:
[...]
[<ffffffff812289b3>] do_sys_poll+0x336/0x6b8
[...]
[<ffffffff81228ed9>] SyS_poll+0xa9/0x194
[...]
Object at ffff88003563fc80, in cache kmalloc-256 size: 256
Allocated:
[...]
Freed:
PID = 617
[...]
[<ffffffff811f034c>] kfree+0xd9/0x166
[<ffffffff814eb60d>] dvb_unregister_device+0xd6/0xe5
[<ffffffff814fa4ed>] dvb_unregister_frontend+0x4b/0x66
[<ffffffff8150810b>] dvb_usb_adapter_frontend_exit+0x69/0xac
[<ffffffff8150617d>] dvb_usb_exit+0x43/0xe5
[<ffffffff81506e90>] dvb_usb_device_exit+0x69/0x7d
[<ffffffff8150a181>] pctv452e_usb_disconnect+0x7b/0x80
Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
---
drivers/media/dvb-core/dvb_frontend.c | 46 ++++++++++++++++++++++-----------
drivers/media/dvb-core/dvb_frontend.h | 1 +
2 files changed, 31 insertions(+), 16 deletions(-)
diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 5bbe389..c38143b4 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -99,8 +99,6 @@ MODULE_PARM_DESC(dvb_mfe_wait_time, "Wait up to <mfe_wait_time> seconds on open(
static DEFINE_MUTEX(frontend_mutex);
struct dvb_frontend_private {
- struct kref refcount;
-
/* thread/frontend values */
struct dvb_device *dvbdev;
struct dvb_frontend_parameters parameters_out;
@@ -138,21 +136,30 @@ struct dvb_frontend_private {
#endif
};
-static void dvb_frontend_private_free(struct kref *ref)
+static void dvb_frontend_invoke_release(struct dvb_frontend *fe,
+ void (*release)(struct dvb_frontend *fe));
+
+static void dvb_frontend_free(struct kref *ref)
{
- struct dvb_frontend_private *fepriv =
- container_of(ref, struct dvb_frontend_private, refcount);
+ struct dvb_frontend *fe =
+ container_of(ref, struct dvb_frontend, refcount);
+ struct dvb_frontend_private *fepriv = fe->frontend_priv;
+
+ dvb_free_device(fepriv->dvbdev);
+
+ dvb_frontend_invoke_release(fe, fe->ops.release);
+
kfree(fepriv);
}
-static void dvb_frontend_private_put(struct dvb_frontend_private *fepriv)
+static void dvb_frontend_put(struct dvb_frontend *fe)
{
- kref_put(&fepriv->refcount, dvb_frontend_private_free);
+ kref_put(&fe->refcount, dvb_frontend_free);
}
-static void dvb_frontend_private_get(struct dvb_frontend_private *fepriv)
+static void dvb_frontend_get(struct dvb_frontend *fe)
{
- kref_get(&fepriv->refcount);
+ kref_get(&fe->refcount);
}
static void dvb_frontend_wakeup(struct dvb_frontend *fe);
@@ -2569,7 +2576,7 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
fepriv->events.eventr = fepriv->events.eventw = 0;
}
- dvb_frontend_private_get(fepriv);
+ dvb_frontend_get(fe);
if (adapter->mfe_shared)
mutex_unlock (&adapter->mfe_lock);
@@ -2619,7 +2626,7 @@ static int dvb_frontend_release(struct inode *inode, struct file *file)
fe->ops.ts_bus_ctrl(fe, 0);
}
- dvb_frontend_private_put(fepriv);
+ dvb_frontend_put(fe);
return ret;
}
@@ -2709,7 +2716,14 @@ int dvb_register_frontend(struct dvb_adapter* dvb,
}
fepriv = fe->frontend_priv;
- kref_init(&fepriv->refcount);
+ kref_init(&fe->refcount);
+
+ /*
+ * After initialization, there need to be two references: one
+ * for dvb_unregister_frontend(), and another one for
+ * dvb_frontend_detach().
+ */
+ dvb_frontend_get(fe);
sema_init(&fepriv->sem, 1);
init_waitqueue_head (&fepriv->wait_queue);
@@ -2744,12 +2758,12 @@ int dvb_unregister_frontend(struct dvb_frontend* fe)
dev_dbg(fe->dvb->device, "%s:\n", __func__);
mutex_lock(&frontend_mutex);
- dvb_frontend_stop (fe);
- dvb_unregister_device (fepriv->dvbdev);
+ dvb_frontend_stop(fe);
+ dvb_remove_device(fepriv->dvbdev);
/* fe is invalid now */
mutex_unlock(&frontend_mutex);
- dvb_frontend_private_put(fepriv);
+ dvb_frontend_put(fe);
return 0;
}
EXPORT_SYMBOL(dvb_unregister_frontend);
@@ -2771,6 +2785,6 @@ void dvb_frontend_detach(struct dvb_frontend* fe)
dvb_frontend_invoke_release(fe, fe->ops.tuner_ops.release);
dvb_frontend_invoke_release(fe, fe->ops.analog_ops.release);
dvb_frontend_invoke_release(fe, fe->ops.detach);
- dvb_frontend_invoke_release(fe, fe->ops.release);
+ dvb_frontend_put(fe);
}
EXPORT_SYMBOL(dvb_frontend_detach);
diff --git a/drivers/media/dvb-core/dvb_frontend.h b/drivers/media/dvb-core/dvb_frontend.h
index d535571..f21b255 100644
--- a/drivers/media/dvb-core/dvb_frontend.h
+++ b/drivers/media/dvb-core/dvb_frontend.h
@@ -667,6 +667,7 @@ struct dtv_frontend_properties {
*/
struct dvb_frontend {
+ struct kref refcount;
struct dvb_frontend_ops ops;
struct dvb_adapter *dvb;
void *demodulator_priv;