On 07/10/2024 16:44, Laurent Pinchart wrote: > Hi Hans, > > On Mon, Oct 07, 2024 at 09:46:47AM +0200, Hans Verkuil wrote: >> Hi Laurent, >> >> Just a reminder: I have extensively reviewed this patch here: >> >> https://lore.kernel.org/linux-media/f4c49ccf-9dc9-475a-8fc9-4ef4c85a729a@xxxxxxxxx/ >> >> and here (specifically checking for mmap() races): >> >> https://lore.kernel.org/linux-media/1a10530f-b4bb-4244-84ff-1f2365ae9b23@xxxxxxxxx/ >> >> To the best of my ability I believe this patch is correct. >> >> Unless you have any additional concerns I plan to take this patch as a fix for >> v6.12 on Monday next week. > > I thought we had an agreement that I could submit an alternative fix for > v6.12. Can you therefore delay merging this patch until v6.12-rc6 ? Correct, if there is indeed something wrong with this patch and an alternative fix is needed (or at least should be considered). But I see nothing wrong with this patch after careful analysis. If you disagree with my analysis, and you think I missed a possible race condition, then that's a reason to wait for a better fix. Otherwise there is no point in waiting any longer. Regards, Hans > >> Alternatively, you can make a PR for 6.12 with this patch that I can pull from. >> >> Regards, >> >> Hans >> >> On 26/09/2024 07:59, Ricardo Ribalda wrote: >>> uvc_unregister_video() can be called asynchronously from >>> uvc_disconnect(). If the device is still streaming when that happens, a >>> plethora of race conditions can occur. >>> >>> Make sure that the device has stopped streaming before exiting this >>> function. >>> >>> If the user still holds handles to the driver's file descriptors, any >>> ioctl will return -ENODEV from the v4l2 core. >>> >>> This change makes uvc more consistent with the rest of the v4l2 drivers >>> using the vb2_fop_* and vb2_ioctl_* helpers. >>> >>> Reviewed-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> >>> Suggested-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> >>> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> >>> --- >>> This patch was part of the series: >>> https://patchwork.linuxtv.org/project/linux-media/list/?series=13064 >>> >>> Moved out from it to ease the review. >>> --- >>> drivers/media/usb/uvc/uvc_driver.c | 32 +++++++++++++++++++++++++++++++- >>> 1 file changed, 31 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c >>> index f0febdc08c2d..bee150b852e4 100644 >>> --- a/drivers/media/usb/uvc/uvc_driver.c >>> +++ b/drivers/media/usb/uvc/uvc_driver.c >>> @@ -1919,11 +1919,41 @@ static void uvc_unregister_video(struct uvc_device *dev) >>> struct uvc_streaming *stream; >>> >>> list_for_each_entry(stream, &dev->streams, list) { >>> + /* Nothing to do here, continue. */ >>> if (!video_is_registered(&stream->vdev)) >>> continue; >>> >>> + /* >>> + * For stream->vdev we follow the same logic as: >>> + * vb2_video_unregister_device(). >>> + */ >>> + >>> + /* 1. Take a reference to vdev */ >>> + get_device(&stream->vdev.dev); >>> + >>> + /* 2. Ensure that no new ioctls can be called. */ >>> video_unregister_device(&stream->vdev); >>> - video_unregister_device(&stream->meta.vdev); >>> + >>> + /* 3. Wait for old ioctls to finish. */ >>> + mutex_lock(&stream->mutex); >>> + >>> + /* 4. Stop streaming. */ >>> + uvc_queue_release(&stream->queue); >>> + >>> + mutex_unlock(&stream->mutex); >>> + >>> + put_device(&stream->vdev.dev); >>> + >>> + /* >>> + * For stream->meta.vdev we can directly call: >>> + * vb2_video_unregister_device(). >>> + */ >>> + vb2_video_unregister_device(&stream->meta.vdev); >>> + >>> + /* >>> + * Now both vdevs are not streaming and all the ioctls will >>> + * return -ENODEV. >>> + */ >>> >>> uvc_debugfs_cleanup_stream(stream); >>> } >>> >>> --- >>> base-commit: 81ee62e8d09ee3c7107d11c8bbfd64073ab601ad >>> change-id: 20240926-uvc_stop_streaming-6e9fd20e97bc >>> >>> Best regards, >> >
