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Subject[ 51/94] udlfb: fix hcd_buffer_free panic on unplug/replug
3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bernie Thompson <bernie@plugable.com>

commit 8d21547d3c9c3bc653261f26d554cfabc4a083de upstream.

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: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/video/udlfb.c | 146 +++++++++++++++++++++++++++-----------------------
include/video/udlfb.h | 1
2 files changed, 81 insertions(+), 66 deletions(-)

--- a/drivers/video/udlfb.c
+++ b/drivers/video/udlfb.c
@@ -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);

@@ -940,35 +936,42 @@ static void dlfb_release_urb_work(struct
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;
- int node = info->node;

- unregister_framebuffer(info);
+ if (info) {
+ int node = info->node;

- 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);
+ unregister_framebuffer(info);

- fb_destroy_modelist(&info->modelist);
+ 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);

- dev->info = 0;
+ dev->info = NULL;

- /* Assume info structure is freed after this point */
- framebuffer_release(info);
+ /* Assume info structure is freed after this point */
+ framebuffer_release(info);

- pr_warn("fb_info for /dev/fb%d has been freed\n", node);
+ 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)
*/
@@ -1570,14 +1573,15 @@ success:
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 */

@@ -1589,9 +1593,7 @@ static int dlfb_usb_probe(struct usb_int
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 * */
@@ -1619,10 +1621,39 @@ static int dlfb_usb_probe(struct usb_int
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");
@@ -1668,15 +1699,13 @@ static int dlfb_usb_probe(struct usb_int
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."
@@ -1684,38 +1713,10 @@ static int dlfb_usb_probe(struct usb_int
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)
@@ -1735,12 +1736,24 @@ static void dlfb_usb_disconnect(struct u
/* When non-active we'll update virtual framebuffer, but no new urbs */
atomic_set(&dev->usb_active, 0);

- /* 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);
- unlink_framebuffer(info);
+ /* 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)
@@ -1806,12 +1819,12 @@ static void dlfb_free_urb_list(struct dl
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;
@@ -1833,6 +1846,7 @@ static void dlfb_free_urb_list(struct dl
kfree(node);
}

+ dev->urbs.count = 0;
}

static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)
--- a/include/video/udlfb.h
+++ b/include/video/udlfb.h
@@ -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 */



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