Index: linux-4.17-rc7/drivers/video/fbdev/udlfb.c
===================================================================
--- linux-4.17-rc7.orig/drivers/video/fbdev/udlfb.c	2018-06-03 13:17:41.000000000 +0200
+++ linux-4.17-rc7/drivers/video/fbdev/udlfb.c	2018-06-03 13:17:41.000000000 +0200
@@ -73,6 +73,13 @@ static bool fb_defio = 1;  /* Detect mma
 static bool shadow = 1; /* Optionally disable shadow framebuffer */
 static int pixel_limit; /* Optionally force a pixel resolution limit */
 
+struct dlfb_deferred_free {
+	struct list_head list;
+	void *mem;
+};
+
+static int dlfb_realloc_framebuffer(struct dlfb_data *dlfb, struct fb_info *info, u32 new_len);
+
 /* dlfb keeps a list of urbs for efficient bulk transfers */
 static void dlfb_urb_completion(struct urb *urb);
 static struct urb *dlfb_get_urb(struct dlfb_data *dlfb);
@@ -927,6 +934,12 @@ static void dlfb_free(struct kref *kref)
 {
 	struct dlfb_data *dlfb = container_of(kref, struct dlfb_data, kref);
 
+	while (!list_empty(&dlfb->deferred_free)) {
+		struct dlfb_deferred_free *d = list_entry(dlfb->deferred_free.next, struct dlfb_deferred_free, list);
+		list_del(&d->list);
+		vfree(d->mem);
+		kfree(d);
+	}
 	vfree(dlfb->backing_buffer);
 	kfree(dlfb->edid);
 	kfree(dlfb);
@@ -1020,10 +1033,6 @@ static int dlfb_ops_check_var(struct fb_
 	struct fb_videomode mode;
 	struct dlfb_data *dlfb = info->par;
 
-	/* TODO: support dynamically changing framebuffer size */
-	if ((var->xres * var->yres * 2) > info->fix.smem_len)
-		return -EINVAL;
-
 	/* set device-specific elements of var unrelated to mode */
 	dlfb_var_color_format(var);
 
@@ -1042,6 +1051,7 @@ static int dlfb_ops_set_par(struct fb_in
 	u16 *pix_framebuffer;
 	int i;
 	struct fb_var_screeninfo fvs;
+	u32 line_length = info->var.xres * (info->var.bits_per_pixel / 8);
 
 	/* clear the activate field because it causes spurious miscompares */
 	fvs = info->var;
@@ -1051,13 +1061,17 @@ static int dlfb_ops_set_par(struct fb_in
 	if (!memcmp(&dlfb->current_mode, &fvs, sizeof(struct fb_var_screeninfo)))
 		return 0;
 
+	result = dlfb_realloc_framebuffer(dlfb, info, info->var.yres * line_length);
+	if (result)
+		return result;
+
 	result = dlfb_set_video_mode(dlfb, &info->var);
 
 	if (result)
 		return result;
 
 	dlfb->current_mode = fvs;
-	info->fix.line_length = info->var.xres * (info->var.bits_per_pixel / 8);
+	info->fix.line_length = line_length;
 
 	if (dlfb->fb_count == 0) {
 
@@ -1066,11 +1080,11 @@ static int dlfb_ops_set_par(struct fb_in
 		pix_framebuffer = (u16 *) info->screen_base;
 		for (i = 0; i < info->fix.smem_len / 2; i++)
 			pix_framebuffer[i] = 0x37e6;
-
-		dlfb_handle_damage(dlfb, 0, 0, info->var.xres, info->var.yres,
-				   info->screen_base);
 	}
 
+	dlfb_handle_damage(dlfb, 0, 0, info->var.xres, info->var.yres,
+			   info->screen_base);
+
 	return 0;
 }
 
@@ -1146,21 +1160,29 @@ static struct fb_ops dlfb_ops = {
 };
 
 
+static void dlfb_deferred_vfree(struct dlfb_data *dlfb, void *mem)
+{
+	struct dlfb_deferred_free *d = kmalloc(sizeof(struct dlfb_deferred_free), GFP_KERNEL);
+	if (!d)
+		return;
+	d->mem = mem;
+	list_add(&d->list, &dlfb->deferred_free);
+}
+
 /*
  * Assumes &info->lock held by caller
  * Assumes no active clients have framebuffer open
  */
-static int dlfb_realloc_framebuffer(struct dlfb_data *dlfb, struct fb_info *info)
+static int dlfb_realloc_framebuffer(struct dlfb_data *dlfb, struct fb_info *info, u32 new_len)
 {
-	int old_len = info->fix.smem_len;
-	int new_len;
+	u32 old_len = info->fix.smem_len;
 	unsigned char *old_fb = info->screen_base;
 	unsigned char *new_fb;
 	unsigned char *new_back = NULL;
 
-	new_len = info->fix.line_length * info->var.yres;
+	new_len = PAGE_ALIGN(new_len);
 
-	if (PAGE_ALIGN(new_len) > old_len) {
+	if (new_len > old_len) {
 		/*
 		 * Alloc system memory for virtual framebuffer
 		 */
@@ -1169,14 +1191,15 @@ static int dlfb_realloc_framebuffer(stru
 			dev_err(info->dev, "Virtual framebuffer alloc failed\n");
 			return -ENOMEM;
 		}
+		memset(new_fb, 0xff, new_len);
 
 		if (info->screen_base) {
 			memcpy(new_fb, old_fb, old_len);
-			vfree(info->screen_base);
+			dlfb_deferred_vfree(dlfb, info->screen_base);
 		}
 
 		info->screen_base = new_fb;
-		info->fix.smem_len = PAGE_ALIGN(new_len);
+		info->fix.smem_len = new_len;
 		info->fix.smem_start = (unsigned long) new_fb;
 		info->flags = udlfb_info_flags;
 
@@ -1192,7 +1215,7 @@ static int dlfb_realloc_framebuffer(stru
 			dev_info(info->dev,
 				 "No shadow/backing buffer allocated\n");
 		else {
-			vfree(dlfb->backing_buffer);
+			dlfb_deferred_vfree(dlfb, dlfb->backing_buffer);
 			dlfb->backing_buffer = new_back;
 		}
 	}
@@ -1344,11 +1367,6 @@ static int dlfb_setup_modes(struct dlfb_
 		 * with mode size info, we can now alloc our framebuffer.
 		 */
 		memcpy(&info->fix, &dlfb_fix, sizeof(dlfb_fix));
-		info->fix.line_length = info->var.xres *
-			(info->var.bits_per_pixel / 8);
-
-		result = dlfb_realloc_framebuffer(dlfb, info);
-
 	} else
 		result = -EINVAL;
 
@@ -1436,7 +1454,10 @@ static ssize_t edid_store(
 	if (!dlfb->edid || memcmp(src, dlfb->edid, src_size))
 		return -EINVAL;
 
-	dlfb_ops_set_par(fb_info);
+	ret = dlfb_ops_set_par(fb_info);
+	if (ret)
+		return ret;
+
 	return src_size;
 }
 
@@ -1596,6 +1617,7 @@ static int dlfb_usb_probe(struct usb_int
 	}
 
 	kref_init(&dlfb->kref); /* matching kref_put in usb .disconnect fn */
+	INIT_LIST_HEAD(&dlfb->deferred_free);
 
 	dlfb->udev = usbdev;
 	usb_set_intfdata(intf, dlfb);
@@ -1693,7 +1715,9 @@ static void dlfb_init_framebuffer_work(s
 	dlfb_select_std_channel(dlfb);
 
 	dlfb_ops_check_var(&info->var, info);
-	dlfb_ops_set_par(info);
+	retval = dlfb_ops_set_par(info);
+	if (retval)
+		goto error;
 
 	retval = register_framebuffer(info);
 	if (retval < 0) {
Index: linux-4.17-rc7/include/video/udlfb.h
===================================================================
--- linux-4.17-rc7.orig/include/video/udlfb.h	2018-06-03 13:17:41.000000000 +0200
+++ linux-4.17-rc7/include/video/udlfb.h	2018-06-03 13:17:41.000000000 +0200
@@ -58,6 +58,7 @@ struct dlfb_data {
 	atomic_t bytes_sent; /* to usb, after compression including overhead */
 	atomic_t cpu_kcycles_used; /* transpired during pixel processing */
 	struct fb_var_screeninfo current_mode;
+	struct list_head deferred_free;
 };
 
 #define NR_USB_REQUEST_I2C_SUB_IO 0x02
