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Commit 8d21547d authored by Bernie Thompson's avatar Bernie Thompson
Browse files

udlfb: fix hcd_buffer_free panic on unplug/replug 



Fix race conditions with unplug/replug behavior, in particular
take care not to hold up USB probe/disconnect for long-running
framebuffer operations and rely on usb to handle teardown.

Fix for kernel panic reported with new F17 multiseat support.

Reported-by: default avatarKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: default avatarBernie Thompson <bernie@plugable.com>
parent 9daee73c

drivers/video/udlfb.c

+80 −66
Original line number Diff line number Diff line
@@ -918,10 +918,6 @@ static void dlfb_free(struct kref *kref) 
{

	struct dlfb_data *dev = container_of(kref, struct dlfb_data, kref);



	/* this function will wait for all in-flight urbs to complete */

	if (dev->urbs.count > 0)

		dlfb_free_urb_list(dev);



	if (dev->backing_buffer)

		vfree(dev->backing_buffer);
@@ -940,11 +936,11 @@ static void dlfb_release_urb_work(struct work_struct *work) 
	up(&unode->dev->urbs.limit_sem);

}



static void dlfb_free_framebuffer_work(struct work_struct *work)

static void dlfb_free_framebuffer(struct dlfb_data *dev)

{

	struct dlfb_data *dev = container_of(work, struct dlfb_data,

					     free_framebuffer_work.work);

	struct fb_info *info = dev->info;



	if (info) {

		int node = info->node;



		unregister_framebuffer(info);
@@ -958,17 +954,24 @@ static void dlfb_free_framebuffer_work(struct work_struct *work) 


		fb_destroy_modelist(&info->modelist);



	dev->info = 0;

		dev->info = NULL;



		/* Assume info structure is freed after this point */

		framebuffer_release(info);



		pr_warn("fb_info for /dev/fb%d has been freed\n", node);

	}



	/* ref taken in probe() as part of registering framebfufer */

	kref_put(&dev->kref, dlfb_free);

}



static void dlfb_free_framebuffer_work(struct work_struct *work)

{

	struct dlfb_data *dev = container_of(work, struct dlfb_data,

					     free_framebuffer_work.work);

	dlfb_free_framebuffer(dev);

}

/*

 * Assumes caller is holding info->lock mutex (for open and release at least)

 */
@@ -1571,14 +1574,15 @@ static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev, 
	kfree(buf);

	return true;

}



static void dlfb_init_framebuffer_work(struct work_struct *work);



static int dlfb_usb_probe(struct usb_interface *interface,

			const struct usb_device_id *id)

{

	struct usb_device *usbdev;

	struct dlfb_data *dev = 0;

	struct fb_info *info = 0;

	int retval = -ENOMEM;

	int i;



	/* usb initialization */
@@ -1590,9 +1594,7 @@ static int dlfb_usb_probe(struct usb_interface *interface, 
		goto error;

	}



	/* we need to wait for both usb and fbdev to spin down on disconnect */

	kref_init(&dev->kref); /* matching kref_put in usb .disconnect fn */

	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */



	dev->udev = usbdev;

	dev->gdev = &usbdev->dev; /* our generic struct device * */
@@ -1620,10 +1622,39 @@ static int dlfb_usb_probe(struct usb_interface *interface, 
		goto error;

	}



	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */



	/* We don't register a new USB class. Our client interface is fbdev */



	/* Workitem keep things fast & simple during USB enumeration */

	INIT_DELAYED_WORK(&dev->init_framebuffer_work,

			  dlfb_init_framebuffer_work);

	schedule_delayed_work(&dev->init_framebuffer_work, 0);



	return 0;



error:

	if (dev) {



		kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */

		kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */



		/* dev has been deallocated. Do not dereference */

	}



	return retval;

}



static void dlfb_init_framebuffer_work(struct work_struct *work)

{

	struct dlfb_data *dev = container_of(work, struct dlfb_data,

					     init_framebuffer_work.work);

	struct fb_info *info;

	int retval;

	int i;



	/* allocates framebuffer driver structure, not framebuffer memory */

	info = framebuffer_alloc(0, &interface->dev);

	info = framebuffer_alloc(0, dev->gdev);

	if (!info) {

		retval = -ENOMEM;

		pr_err("framebuffer_alloc failed\n");
@@ -1669,15 +1700,13 @@ static int dlfb_usb_probe(struct usb_interface *interface, 
	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++) {

		retval = device_create_file(info->dev, &fb_device_attrs[i]);

		if (retval) {

			pr_err("device_create_file failed %d\n", retval);

			goto err_del_attrs;

			pr_warn("device_create_file failed %d\n", retval);

		}

	}



	retval = device_create_bin_file(info->dev, &edid_attr);

	if (retval) {

		pr_err("device_create_bin_file failed %d\n", retval);

		goto err_del_attrs;

		pr_warn("device_create_bin_file failed %d\n", retval);

	}



	pr_info("DisplayLink USB device /dev/fb%d attached. %dx%d resolution."
@@ -1685,38 +1714,10 @@ static int dlfb_usb_probe(struct usb_interface *interface, 
			info->var.xres, info->var.yres,

			((dev->backing_buffer) ?

			info->fix.smem_len * 2 : info->fix.smem_len) >> 10);

	return 0;



err_del_attrs:

	for (i -= 1; i >= 0; i--)

		device_remove_file(info->dev, &fb_device_attrs[i]);

	return;



error:

	if (dev) {



		if (info) {

			if (info->cmap.len != 0)

				fb_dealloc_cmap(&info->cmap);

			if (info->monspecs.modedb)

				fb_destroy_modedb(info->monspecs.modedb);

			if (info->screen_base)

				vfree(info->screen_base);



			fb_destroy_modelist(&info->modelist);



			framebuffer_release(info);

		}



		if (dev->backing_buffer)

			vfree(dev->backing_buffer);



		kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */

		kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */



		/* dev has been deallocated. Do not dereference */

	}



	return retval;

	dlfb_free_framebuffer(dev);

}



static void dlfb_usb_disconnect(struct usb_interface *interface)
@@ -1736,12 +1737,24 @@ static void dlfb_usb_disconnect(struct usb_interface *interface) 
	/* When non-active we'll update virtual framebuffer, but no new urbs */

	atomic_set(&dev->usb_active, 0);



	/* this function will wait for all in-flight urbs to complete */

	dlfb_free_urb_list(dev);



	if (info) {



		/* remove udlfb's sysfs interfaces */

		for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)

			device_remove_file(info->dev, &fb_device_attrs[i]);

		device_remove_bin_file(info->dev, &edid_attr);



		/* it's safe to uncomment next line if your kernel

		   doesn't yet have this function exported */

		unlink_framebuffer(info);

	}



	usb_set_intfdata(interface, NULL);

	dev->udev = NULL;

	dev->gdev = NULL;



	/* if clients still have us open, will be freed on last close */

	if (dev->fb_count == 0)
@@ -1807,12 +1820,12 @@ static void dlfb_free_urb_list(struct dlfb_data *dev) 
	int ret;

	unsigned long flags;



	pr_notice("Waiting for completes and freeing all render urbs\n");

	pr_notice("Freeing all render urbs\n");



	/* keep waiting and freeing, until we've got 'em all */

	while (count--) {



		/* Getting interrupted means a leak, but ok at shutdown*/

		/* Getting interrupted means a leak, but ok at disconnect */

		ret = down_interruptible(&dev->urbs.limit_sem);

		if (ret)

			break;
@@ -1834,6 +1847,7 @@ static void dlfb_free_urb_list(struct dlfb_data *dev) 
		kfree(node);

	}



	dev->urbs.count = 0;

}



static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)

include/video/udlfb.h

+1 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ struct dlfb_data { 
	char *backing_buffer;

	int fb_count;

	bool virtualized; /* true when physical usb device not present */

	struct delayed_work init_framebuffer_work;

	struct delayed_work free_framebuffer_work;

	atomic_t usb_active; /* 0 = update virtual buffer, but no usb traffic */

	atomic_t lost_pixels; /* 1 = a render op failed. Need screen refresh */