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Subject[PATCH 4.19 151/152] udlfb: handle unplug properly
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

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

From: Mikulas Patocka <mpatocka@redhat.com>

commit 68a958a915ca912b8ce71b9eea7445996f6e681e upstream.

The udlfb driver maintained an open count and cleaned up itself when the
count reached zero. But the console is also counted in the reference count
- so, if the user unplugged the device, the open count would not drop to
zero and the driver stayed loaded with console attached. If the user
re-plugged the adapter, it would create a device /dev/fb1, show green
screen and the access to the console would be lost.

The framebuffer subsystem has reference counting on its own - in order to
fix the unplug bug, we rely the framebuffer reference counting. When the
user unplugs the adapter, we call unregister_framebuffer unconditionally.
unregister_framebuffer will unbind the console, wait until all users stop
using the framebuffer and then call the fb_destroy method. The fb_destroy
cleans up the USB driver.

This patch makes the following changes:
* Drop dlfb->kref and rely on implicit framebuffer reference counting
instead.
* dlfb_usb_disconnect calls unregister_framebuffer, the rest of driver
cleanup is done in the function dlfb_ops_destroy. dlfb_ops_destroy will
be called by the framebuffer subsystem when no processes have the
framebuffer open or mapped.
* We don't use workqueue during initialization, but initialize directly
from dlfb_usb_probe. The workqueue could race with dlfb_usb_disconnect
and this racing would produce various kinds of memory corruption.
* We use usb_get_dev and usb_put_dev to make sure that the USB subsystem
doesn't free the device under us.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
cc: Dave Airlie <airlied@redhat.com>
Cc: Bernie Thompson <bernie@plugable.com>,
Cc: Ladislav Michl <ladis@linux-mips.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/video/fbdev/udlfb.c | 141 +++++++++++---------------------------------
include/video/udlfb.h | 3
2 files changed, 37 insertions(+), 107 deletions(-)

--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -916,8 +916,6 @@ static int dlfb_ops_open(struct fb_info

dlfb->fb_count++;

- kref_get(&dlfb->kref);
-
if (fb_defio && (info->fbdefio == NULL)) {
/* enable defio at last moment if not disabled by client */

@@ -940,14 +938,17 @@ static int dlfb_ops_open(struct fb_info
return 0;
}

-/*
- * Called when all client interfaces to start transactions have been disabled,
- * and all references to our device instance (dlfb_data) are released.
- * Every transaction must have a reference, so we know are fully spun down
- */
-static void dlfb_free(struct kref *kref)
+static void dlfb_ops_destroy(struct fb_info *info)
{
- struct dlfb_data *dlfb = container_of(kref, struct dlfb_data, kref);
+ struct dlfb_data *dlfb = info->par;
+
+ if (info->cmap.len != 0)
+ fb_dealloc_cmap(&info->cmap);
+ if (info->monspecs.modedb)
+ fb_destroy_modedb(info->monspecs.modedb);
+ vfree(info->screen_base);
+
+ fb_destroy_modelist(&info->modelist);

while (!list_empty(&dlfb->deferred_free)) {
struct dlfb_deferred_free *d = list_entry(dlfb->deferred_free.next, struct dlfb_deferred_free, list);
@@ -957,40 +958,13 @@ static void dlfb_free(struct kref *kref)
}
vfree(dlfb->backing_buffer);
kfree(dlfb->edid);
+ usb_put_dev(dlfb->udev);
kfree(dlfb);
-}
-
-static void dlfb_free_framebuffer(struct dlfb_data *dlfb)
-{
- struct fb_info *info = dlfb->info;
-
- if (info) {
- unregister_framebuffer(info);
-
- if (info->cmap.len != 0)
- fb_dealloc_cmap(&info->cmap);
- if (info->monspecs.modedb)
- fb_destroy_modedb(info->monspecs.modedb);
- vfree(info->screen_base);
-
- fb_destroy_modelist(&info->modelist);
-
- dlfb->info = NULL;
-
- /* Assume info structure is freed after this point */
- framebuffer_release(info);
- }

- /* ref taken in probe() as part of registering framebfufer */
- kref_put(&dlfb->kref, dlfb_free);
+ /* Assume info structure is freed after this point */
+ framebuffer_release(info);
}

-static void dlfb_free_framebuffer_work(struct work_struct *work)
-{
- struct dlfb_data *dlfb = container_of(work, struct dlfb_data,
- free_framebuffer_work.work);
- dlfb_free_framebuffer(dlfb);
-}
/*
* Assumes caller is holding info->lock mutex (for open and release at least)
*/
@@ -1000,10 +974,6 @@ static int dlfb_ops_release(struct fb_in

dlfb->fb_count--;

- /* We can't free fb_info here - fbmem will touch it when we return */
- if (dlfb->virtualized && (dlfb->fb_count == 0))
- schedule_delayed_work(&dlfb->free_framebuffer_work, HZ);
-
if ((dlfb->fb_count == 0) && (info->fbdefio)) {
fb_deferred_io_cleanup(info);
kfree(info->fbdefio);
@@ -1013,8 +983,6 @@ static int dlfb_ops_release(struct fb_in

dev_dbg(info->dev, "release, user=%d count=%d\n", user, dlfb->fb_count);

- kref_put(&dlfb->kref, dlfb_free);
-
return 0;
}

@@ -1172,6 +1140,7 @@ static struct fb_ops dlfb_ops = {
.fb_blank = dlfb_ops_blank,
.fb_check_var = dlfb_ops_check_var,
.fb_set_par = dlfb_ops_set_par,
+ .fb_destroy = dlfb_ops_destroy,
};


@@ -1615,12 +1584,13 @@ success:
return true;
}

-static void dlfb_init_framebuffer_work(struct work_struct *work);
-
static int dlfb_usb_probe(struct usb_interface *intf,
const struct usb_device_id *id)
{
+ int i;
+ const struct device_attribute *attr;
struct dlfb_data *dlfb;
+ struct fb_info *info;
int retval = -ENOMEM;
struct usb_device *usbdev = interface_to_usbdev(intf);

@@ -1631,10 +1601,9 @@ static int dlfb_usb_probe(struct usb_int
goto error;
}

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

- dlfb->udev = usbdev;
+ dlfb->udev = usb_get_dev(usbdev);
usb_set_intfdata(intf, dlfb);

dev_dbg(&intf->dev, "console enable=%d\n", console);
@@ -1657,42 +1626,6 @@ static int dlfb_usb_probe(struct usb_int
}


- if (!dlfb_alloc_urb_list(dlfb, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
- retval = -ENOMEM;
- dev_err(&intf->dev, "unable to allocate urb list\n");
- goto error;
- }
-
- kref_get(&dlfb->kref); /* matching kref_put in free_framebuffer_work */
-
- /* We don't register a new USB class. Our client interface is dlfbev */
-
- /* Workitem keep things fast & simple during USB enumeration */
- INIT_DELAYED_WORK(&dlfb->init_framebuffer_work,
- dlfb_init_framebuffer_work);
- schedule_delayed_work(&dlfb->init_framebuffer_work, 0);
-
- return 0;
-
-error:
- if (dlfb) {
-
- kref_put(&dlfb->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)
-{
- int i, retval;
- struct fb_info *info;
- const struct device_attribute *attr;
- struct dlfb_data *dlfb = container_of(work, struct dlfb_data,
- init_framebuffer_work.work);
-
/* allocates framebuffer driver structure, not framebuffer memory */
info = framebuffer_alloc(0, &dlfb->udev->dev);
if (!info) {
@@ -1706,17 +1639,22 @@ static void dlfb_init_framebuffer_work(s
dlfb->ops = dlfb_ops;
info->fbops = &dlfb->ops;

+ INIT_LIST_HEAD(&info->modelist);
+
+ if (!dlfb_alloc_urb_list(dlfb, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
+ retval = -ENOMEM;
+ dev_err(&intf->dev, "unable to allocate urb list\n");
+ goto error;
+ }
+
+ /* We don't register a new USB class. Our client interface is dlfbev */
+
retval = fb_alloc_cmap(&info->cmap, 256, 0);
if (retval < 0) {
dev_err(info->device, "cmap allocation failed: %d\n", retval);
goto error;
}

- INIT_DELAYED_WORK(&dlfb->free_framebuffer_work,
- dlfb_free_framebuffer_work);
-
- INIT_LIST_HEAD(&info->modelist);
-
retval = dlfb_setup_modes(dlfb, info, NULL, 0);
if (retval != 0) {
dev_err(info->device,
@@ -1760,10 +1698,16 @@ static void dlfb_init_framebuffer_work(s
dev_name(info->dev), info->var.xres, info->var.yres,
((dlfb->backing_buffer) ?
info->fix.smem_len * 2 : info->fix.smem_len) >> 10);
- return;
+ return 0;

error:
- dlfb_free_framebuffer(dlfb);
+ if (dlfb->info) {
+ dlfb_ops_destroy(dlfb->info);
+ } else if (dlfb) {
+ usb_put_dev(dlfb->udev);
+ kfree(dlfb);
+ }
+ return retval;
}

static void dlfb_usb_disconnect(struct usb_interface *intf)
@@ -1791,20 +1735,9 @@ static void dlfb_usb_disconnect(struct u
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);
}

- usb_set_intfdata(intf, NULL);
- dlfb->udev = NULL;
-
- /* if clients still have us open, will be freed on last close */
- if (dlfb->fb_count == 0)
- schedule_delayed_work(&dlfb->free_framebuffer_work, 0);
-
- /* release reference taken by kref_init in probe() */
- kref_put(&dlfb->kref, dlfb_free);
-
- /* consider dlfb_data freed */
+ unregister_framebuffer(info);
}

static struct usb_driver dlfb_driver = {
--- a/include/video/udlfb.h
+++ b/include/video/udlfb.h
@@ -36,12 +36,9 @@ struct dlfb_data {
struct usb_device *udev;
struct fb_info *info;
struct urb_list urbs;
- struct kref kref;
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 */
char *edid; /* null until we read edid from hw or get from sysfs */

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