The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x 619d9b710cf06f7a00a17120ca92333684ac45a8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '167810021760137@kroah.com' --subject-prefix 'PATCH 4.19.y' HEAD^..
Possible dependencies:
619d9b710cf0 ("media: uvcvideo: Fix race condition with usb_kill_urb") 40140eda661e ("media: uvcvideo: Implement mask for V4L2_CTRL_TYPE_MENU") adfd3910c27f ("media: uvcvideo: Remove void casting for the status endpoint") 382075604a68 ("media: uvcvideo: Limit power line control for Quanta UVC Webcam") 710871163510 ("media: uvcvideo: Add missing value for power_line_frequency") 70fa906d6fce ("media: uvcvideo: Use control names from framework") 9b31ea808a44 ("media: uvcvideo: Add support for V4L2_CTRL_TYPE_CTRL_CLASS") 866c6bdd5663 ("media: uvcvideo: refactor __uvc_ctrl_add_mapping") 9e56380ae625 ("media: uvcvideo: Rename debug functions") ed4c5fa4d804 ("media: uvcvideo: use dev_printk() for uvc_trace()") 59e92bf62771 ("media: uvcvideo: New macro uvc_trace_cont") 69df09547e7a ("media: uvcvideo: Use dev_ printk aliases") 6f6a87eb8266 ("media: uvcvideo: Add Privacy control based on EXT_GPIO") 2886477ff987 ("media: uvcvideo: Implement UVC_EXT_GPIO_UNIT") d9c8763e6129 ("media: uvcvideo: Provide sync and async uvc_ctrl_status_event") 351509c604dc ("media: uvcvideo: Move guid to entity") dc9455ffae02 ("media: uvcvideo: Accept invalid bFormatIndex and bFrameIndex values") b400b6f28af0 ("media: uvcvideo: Force UVC version to 1.0a for 1bcf:0b40") 8a652a17e3c0 ("media: uvcvideo: Ensure all probed info is returned to v4l2") f875bcc375c7 ("media: uvcvideo: Fix dereference of out-of-bound list iterator")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 619d9b710cf06f7a00a17120ca92333684ac45a8 Mon Sep 17 00:00:00 2001 From: Ricardo Ribalda ribalda@chromium.org Date: Thu, 5 Jan 2023 15:31:29 +0100 Subject: [PATCH] media: uvcvideo: Fix race condition with usb_kill_urb
usb_kill_urb warranties that all the handlers are finished when it returns, but does not protect against threads that might be handling asynchronously the urb.
For UVC, the function uvc_ctrl_status_event_async() takes care of control changes asynchronously.
If the code is executed in the following order:
CPU 0 CPU 1 ===== ===== uvc_status_complete() uvc_status_stop() uvc_ctrl_status_event_work() uvc_status_start() -> FAIL
Then uvc_status_start will keep failing and this error will be shown:
<4>[ 5.540139] URB 0000000000000000 submitted while active drivers/usb/core/urb.c:378 usb_submit_urb+0x4c3/0x528
Let's improve the current situation, by not re-submiting the urb if we are stopping the status event. Also process the queued work (if any) during stop.
CPU 0 CPU 1 ===== ===== uvc_status_complete() uvc_status_stop() uvc_status_start() uvc_ctrl_status_event_work() -> FAIL
Hopefully, with the usb layer protection this should be enough to cover all the cases.
Cc: stable@vger.kernel.org Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives") Reviewed-by: Yunke Cao yunkec@chromium.org Signed-off-by: Ricardo Ribalda ribalda@chromium.org Reviewed-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Laurent Pinchart laurent.pinchart@ideasonboard.com
diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c index ee58f0db2763..c3aeba3fe31b 100644 --- a/drivers/media/usb/uvc/uvc_ctrl.c +++ b/drivers/media/usb/uvc/uvc_ctrl.c @@ -6,6 +6,7 @@ * Laurent Pinchart (laurent.pinchart@ideasonboard.com) */
+#include <asm/barrier.h> #include <linux/bitops.h> #include <linux/kernel.h> #include <linux/list.h> @@ -1571,6 +1572,10 @@ static void uvc_ctrl_status_event_work(struct work_struct *work)
uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
+ /* The barrier is needed to synchronize with uvc_status_stop(). */ + if (smp_load_acquire(&dev->flush_status)) + return; + /* Resubmit the URB. */ w->urb->interval = dev->int_ep->desc.bInterval; ret = usb_submit_urb(w->urb, GFP_KERNEL); diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c index 602830a8023e..a78a88c710e2 100644 --- a/drivers/media/usb/uvc/uvc_status.c +++ b/drivers/media/usb/uvc/uvc_status.c @@ -6,6 +6,7 @@ * Laurent Pinchart (laurent.pinchart@ideasonboard.com) */
+#include <asm/barrier.h> #include <linux/kernel.h> #include <linux/input.h> #include <linux/slab.h> @@ -311,5 +312,41 @@ int uvc_status_start(struct uvc_device *dev, gfp_t flags)
void uvc_status_stop(struct uvc_device *dev) { + struct uvc_ctrl_work *w = &dev->async_ctrl; + + /* + * Prevent the asynchronous control handler from requeing the URB. The + * barrier is needed so the flush_status change is visible to other + * CPUs running the asynchronous handler before usb_kill_urb() is + * called below. + */ + smp_store_release(&dev->flush_status, true); + + /* + * Cancel any pending asynchronous work. If any status event was queued, + * process it synchronously. + */ + if (cancel_work_sync(&w->work)) + uvc_ctrl_status_event(w->chain, w->ctrl, w->data); + + /* Kill the urb. */ usb_kill_urb(dev->int_urb); + + /* + * The URB completion handler may have queued asynchronous work. This + * won't resubmit the URB as flush_status is set, but it needs to be + * cancelled before returning or it could then race with a future + * uvc_status_start() call. + */ + if (cancel_work_sync(&w->work)) + uvc_ctrl_status_event(w->chain, w->ctrl, w->data); + + /* + * From this point, there are no events on the queue and the status URB + * is dead. No events will be queued until uvc_status_start() is called. + * The barrier is needed to make sure that flush_status is visible to + * uvc_ctrl_status_event_work() when uvc_status_start() will be called + * again. + */ + smp_store_release(&dev->flush_status, false); } diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index e85df8deb965..c0e706fcd2cb 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -577,6 +577,7 @@ struct uvc_device { struct usb_host_endpoint *int_ep; struct urb *int_urb; struct uvc_status *status; + bool flush_status;
struct input_dev *input; char input_phys[64];