[PATCH 5.10 66/66] usb: gadget: uvc: allow for application to cleanly shutdown

Greg Kroah-Hartman
2022-05-16T19:55:13Z

From: Dan Vacura <w36195@motorola.com>

commit b81ac4395bbeaf36e078dea1a48c02dd97b76235 upstream.

Several types of kernel panics can occur due to timing during the uvc
gadget removal. This appears to be a problem with gadget resources being
managed by both the client application's v4l2 open/close and the UDC
gadget bind/unbind. Since the concept of USB_GADGET_DELAYED_STATUS
doesn't exist for unbind, add a wait to allow for the application to
close out.

Some examples of the panics that can occur are:

<1>[ 1147.652313] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000028
<4>[ 1147.652510] Call trace:
<4>[ 1147.652514] usb_gadget_disconnect+0x74/0x1f0
<4>[ 1147.652516] usb_gadget_deactivate+0x38/0x168
<4>[ 1147.652520] usb_function_deactivate+0x54/0x90
<4>[ 1147.652524] uvc_function_disconnect+0x14/0x38
<4>[ 1147.652527] uvc_v4l2_release+0x34/0xa0
<4>[ 1147.652537] __fput+0xdc/0x2c0
<4>[ 1147.652540] ____fput+0x10/0x1c
<4>[ 1147.652545] task_work_run+0xe4/0x12c
<4>[ 1147.652549] do_notify_resume+0x108/0x168

<1>[ 282.950561][ T1472] Unable to handle kernel NULL pointer
dereference at virtual address 00000000000005b8
<6>[ 282.953111][ T1472] Call trace:
<6>[ 282.953121][ T1472] usb_function_deactivate+0x54/0xd4
<6>[ 282.953134][ T1472] uvc_v4l2_release+0xac/0x1e4
<6>[ 282.953145][ T1472] v4l2_release+0x134/0x1f0
<6>[ 282.953167][ T1472] __fput+0xf4/0x428
<6>[ 282.953178][ T1472] ____fput+0x14/0x24
<6>[ 282.953193][ T1472] task_work_run+0xac/0x130

<3>[ 213.410077][ T29] configfs-gadget gadget: uvc: Failed to queue
request (-108).
<1>[ 213.410116][ T29] Unable to handle kernel NULL pointer
dereference at virtual address 0000000000000003
<6>[ 213.413460][ T29] Call trace:
<6>[ 213.413474][ T29] uvcg_video_pump+0x1f0/0x384
<6>[ 213.413489][ T29] process_one_work+0x2a4/0x544
<6>[ 213.413502][ T29] worker_thread+0x350/0x784
<6>[ 213.413515][ T29] kthread+0x2ac/0x320
<6>[ 213.413528][ T29] ret_from_fork+0x10/0x30

Signed-off-by: Dan Vacura <w36195@motorola.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220503201039.71720-1-w36195@motorola.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_uvc.c | 25 +++++++++++++++++++++++++
drivers/usb/gadget/function/uvc.h | 2 ++
drivers/usb/gadget/function/uvc_v4l2.c | 3 ++-
3 files changed, 29 insertions(+), 1 deletion(-)

--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -888,13 +888,37 @@ static void uvc_function_unbind(struct u
{
struct usb_composite_dev *cdev = c->cdev;
struct uvc_device *uvc = to_uvc(f);
+ long wait_ret = 1;

uvcg_info(f, "%s()\n", __func__);

+ /* If we know we're connected via v4l2, then there should be a cleanup
+ * of the device from userspace either via UVC_EVENT_DISCONNECT or
+ * though the video device removal uevent. Allow some time for the
+ * application to close out before things get deleted.
+ */
+ if (uvc->func_connected) {
+ uvcg_dbg(f, "waiting for clean disconnect\n");
+ wait_ret = wait_event_interruptible_timeout(uvc->func_connected_queue,
+ uvc->func_connected == false, msecs_to_jiffies(500));
+ uvcg_dbg(f, "done waiting with ret: %ld\n", wait_ret);
+ }
+
device_remove_file(&uvc->vdev.dev, &dev_attr_function_name);
video_unregister_device(&uvc->vdev);
v4l2_device_unregister(&uvc->v4l2_dev);

+ if (uvc->func_connected) {
+ /* Wait for the release to occur to ensure there are no longer any
+ * pending operations that may cause panics when resources are cleaned
+ * up.
+ */
+ uvcg_warn(f, "%s no clean disconnect, wait for release\n", __func__);
+ wait_ret = wait_event_interruptible_timeout(uvc->func_connected_queue,
+ uvc->func_connected == false, msecs_to_jiffies(1000));
+ uvcg_dbg(f, "done waiting for release with ret: %ld\n", wait_ret);
+ }
+
usb_ep_free_request(cdev->gadget->ep0, uvc->control_req);
kfree(uvc->control_buf);

@@ -913,6 +937,7 @@ static struct usb_function *uvc_alloc(st

mutex_init(&uvc->video.mutex);
uvc->state = UVC_STATE_DISCONNECTED;
+ init_waitqueue_head(&uvc->func_connected_queue);
opts = fi_to_f_uvc_opts(fi);

mutex_lock(&opts->lock);
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -14,6 +14,7 @@
#include <linux/spinlock.h>
#include <linux/usb/composite.h>
#include <linux/videodev2.h>
+#include <linux/wait.h>

#include <media/v4l2-device.h>
#include <media/v4l2-dev.h>
@@ -118,6 +119,7 @@ struct uvc_device {
struct usb_function func;
struct uvc_video video;
bool func_connected;
+ wait_queue_head_t func_connected_queue;

/* Descriptors */
struct {
--- a/drivers/usb/gadget/function/uvc_v4l2.c
+++ b/drivers/usb/gadget/function/uvc_v4l2.c
@@ -252,10 +252,11 @@ uvc_v4l2_subscribe_event(struct v4l2_fh

static void uvc_v4l2_disable(struct uvc_device *uvc)
{
- uvc->func_connected = false;
uvc_function_disconnect(uvc);
uvcg_video_enable(&uvc->video, 0);
uvcg_free_buffers(&uvc->video.queue);
+ uvc->func_connected = false;
+ wake_up_interruptible(&uvc->func_connected_queue);
}

static int