linux-kernel - [PATCH v5 0/3] uvcvideo: Attempt N to land UVC race conditions fixes

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Date:   Wed, 22 Nov 2023 11:45:46 +0000
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Tomasz Figa <tfiga@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sean Paul <seanpaul@...omium.org>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: [PATCH v5 0/3] uvcvideo: Attempt N to land UVC race conditions
 fixes

Back in 2020 Guenter published a set of patches to fix some race
conditions on UVC.
https://lore.kernel.org/all/20200917022547.198090-5-linux@roeck-us.net/

That kind of race conditions are not only seen on UVC, but are a common
sin on almost all the kernel, so this is what it was decided back then
that we should try to fix them at higher levels.

After that. A lot of video_is_registered() were added to the core:

```
ribalda@...o:~/work/linux$ git grep is_registered drivers/media/v4l2-core/
drivers/media/v4l2-core/v4l2-compat-ioctl32.c:  if (!video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev)) {
drivers/media/v4l2-core/v4l2-dev.c:             if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (!video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (vdev == NULL || !video_is_registered(vdev)) {
drivers/media/v4l2-core/v4l2-dev.c:             if (video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-dev.c:     if (!vdev || !video_is_registered(vdev))
drivers/media/v4l2-core/v4l2-ioctl.c:   if (!video_is_registered(vfd)) {
drivers/media/v4l2-core/v4l2-subdev.c:  if (video_is_registered(vdev)) {
```

And recently Sakari is trying to land:
https://lore.kernel.org/linux-media/20230201214535.347075-1-sakari.ailus@linux.intel.com/

Which will make obsolete a lot of (all?) of the video_is_registered() checks on
Guenter's patches.

Besides those checks, there were some other valid races fixed on his
patches.

This series is just a rebase of what I think is missing on UVC even
if we fixed v4l2/core with all the video_is_register() checks removed.

I have tested the series with lockdep and a loop of authorize/de-authorize
while steaming.

Thanks!

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
Changes in v5:
- Some code from 2/3 ended in 3/3... Sorry about that.
- Link to v4: https://lore.kernel.org/r/20231122-guenter-mini-v4-0-3d94e1e34dc1@chromium.org

Changes in v4 Thanks Sergey!:
- Reorder patches
- Improve commit messages
- Do not process async work on exit.
- Link to v3: https://lore.kernel.org/r/20231121-guenter-mini-v3-0-d8a5eae2312b@chromium.org

Changes in v3:
- Introduce media: uvcvideo: Do not halt the device after disconnect
- Introduce media: uvcvideo: Always use uvc_status_stop()
- Link to v2: https://lore.kernel.org/r/20230309-guenter-mini-v2-0-e6410d590d43@chromium.org

Changes in v2:
- Actually send the series to the ML an not only to individuals.
- Link to v1: https://lore.kernel.org/r/20230309-guenter-mini-v1-0-627d10cf6e96@chromium.org

---
Guenter Roeck (1):
      media: uvcvideo: Lock video streams and queues while unregistering

Ricardo Ribalda (2):
      media: uvcvideo: Always use uvc_status_stop()
      media: uvcvideo: Do not use usb_* functions after .disconnect

 drivers/media/usb/uvc/uvc_ctrl.c   |  4 ----
 drivers/media/usb/uvc/uvc_driver.c | 13 ++++++++++-
 drivers/media/usb/uvc/uvc_status.c |  8 +++----
 drivers/media/usb/uvc/uvc_v4l2.c   |  2 +-
 drivers/media/usb/uvc/uvc_video.c  | 45 ++++++++++++++++++++++++--------------
 drivers/media/usb/uvc/uvcvideo.h   |  4 +++-
 6 files changed, 48 insertions(+), 28 deletions(-)
---
base-commit: 98b1cc82c4affc16f5598d4fa14b1858671b2263
change-id: 20230309-guenter-mini-89861b084ef1

Best regards,
-- 
Ricardo Ribalda <ribalda@...omium.org>