New subject: [PATCH 6.2.y] media: uvcvideo: Fix race condition with usb_kill_urb

6 Mar 2023

The patch below does not apply to the 6.2-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-6.2.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 '16781002113959@kroah.com' --subject-prefix 'PATCH 6.2.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")
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];

    

FAILED: patch "[PATCH] media: uvcvideo: Fix race condition with usb_kill_urb" failed to apply to 6.2-stable tree