fbdev fixes and updates for kernel v5.19-rc6:

fbcon now prevents switching to screen resolutions which are smaller
 than the font size, and prevents enabling a font which is bigger than
 the current screen resolution. This fixes vmalloc-out-of-bounds accesses
 found by KASAN.
 
 Guiling Deng fixed a bug where the centered fbdev logo wasn't displayed
 correctly if the screen size matched the logo size.
 
 Hsin-Yi Wang provided a patch to include errno.h to fix build when
 CONFIG_OF isn't enabled.
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Merge tag 'for-5.19/fbdev-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev

Pull fbdev fixes from Helge Deller:

 - fbcon now prevents switching to screen resolutions which are smaller
   than the font size, and prevents enabling a font which is bigger than
   the current screen resolution. This fixes vmalloc-out-of-bounds
   accesses found by KASAN.

 - Guiling Deng fixed a bug where the centered fbdev logo wasn't
   displayed correctly if the screen size matched the logo size.

 - Hsin-Yi Wang provided a patch to include errno.h to fix build when
   CONFIG_OF isn't enabled.

* tag 'for-5.19/fbdev-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev:
  fbcon: Use fbcon_info_from_console() in fbcon_modechange_possible()
  fbmem: Check virtual screen sizes in fb_set_var()
  fbcon: Prevent that screen size is smaller than font size
  fbcon: Disallow setting font bigger than screen size
  video: of_display_timing.h: include errno.h
  fbdev: fbmem: Fix logo center image dx issue

drivers/video/fbdev/core/fbcon.c

@@ -2469,6 +2469,11 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font,
 	if (charcount != 256 && charcount != 512)
 		return -EINVAL;
 
+	/* font bigger than screen resolution ? */
+	if (w > FBCON_SWAP(info->var.rotate, info->var.xres, info->var.yres) ||
+	    h > FBCON_SWAP(info->var.rotate, info->var.yres, info->var.xres))
+		return -EINVAL;
+
 	/* Make sure drawing engine can handle the font */
 	if (!(info->pixmap.blit_x & (1 << (font->width - 1))) ||
 	    !(info->pixmap.blit_y & (1 << (font->height - 1))))
@@ -2731,6 +2736,34 @@ void fbcon_update_vcs(struct fb_info *info, bool all)
 }
 EXPORT_SYMBOL(fbcon_update_vcs);
 
+/* let fbcon check if it supports a new screen resolution */
+int fbcon_modechange_possible(struct fb_info *info, struct fb_var_screeninfo *var)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct vc_data *vc;
+	unsigned int i;
+
+	WARN_CONSOLE_UNLOCKED();
+
+	if (!ops)
+		return 0;
+
+	/* prevent setting a screen size which is smaller than font size */
+	for (i = first_fb_vc; i <= last_fb_vc; i++) {
+		vc = vc_cons[i].d;
+		if (!vc || vc->vc_mode != KD_TEXT ||
+			   fbcon_info_from_console(i) != info)
+			continue;
+
+		if (vc->vc_font.width  > FBCON_SWAP(var->rotate, var->xres, var->yres) ||
+		    vc->vc_font.height > FBCON_SWAP(var->rotate, var->yres, var->xres))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fbcon_modechange_possible);
+
 int fbcon_mode_deleted(struct fb_info *info,
 		       struct fb_videomode *mode)
 {

drivers/video/fbdev/core/fbmem.c

@@ -511,7 +511,7 @@ static int fb_show_logo_line(struct fb_info *info, int rotate,
 
 		while (n && (n * (logo->width + 8) - 8 > xres))
 			--n;
-		image.dx = (xres - n * (logo->width + 8) - 8) / 2;
+		image.dx = (xres - (n * (logo->width + 8) - 8)) / 2;
 		image.dy = y ?: (yres - logo->height) / 2;
 	} else {
 		image.dx = 0;
@@ -1017,6 +1017,16 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 	if (ret)
 		return ret;
 
+	/* verify that virtual resolution >= physical resolution */
+	if (var->xres_virtual < var->xres ||
+	    var->yres_virtual < var->yres) {
+		pr_warn("WARNING: fbcon: Driver '%s' missed to adjust virtual screen size (%ux%u vs. %ux%u)\n",
+			info->fix.id,
+			var->xres_virtual, var->yres_virtual,
+			var->xres, var->yres);
+		return -EINVAL;
+	}
+
 	if ((var->activate & FB_ACTIVATE_MASK) != FB_ACTIVATE_NOW)
 		return 0;
 
@@ -1107,7 +1117,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
 			return -EFAULT;
 		console_lock();
 		lock_fb_info(info);
-		ret = fb_set_var(info, &var);
+		ret = fbcon_modechange_possible(info, &var);
+		if (!ret)
+			ret = fb_set_var(info, &var);
 		if (!ret)
 			fbcon_update_vcs(info, var.activate & FB_ACTIVATE_ALL);
 		unlock_fb_info(info);

include/linux/fbcon.h

@@ -15,6 +15,8 @@ void fbcon_new_modelist(struct fb_info *info);
 void fbcon_get_requirement(struct fb_info *info,
 			   struct fb_blit_caps *caps);
 void fbcon_fb_blanked(struct fb_info *info, int blank);
+int  fbcon_modechange_possible(struct fb_info *info,
+			       struct fb_var_screeninfo *var);
 void fbcon_update_vcs(struct fb_info *info, bool all);
 void fbcon_remap_all(struct fb_info *info);
 int fbcon_set_con2fb_map_ioctl(void __user *argp);
@@ -33,6 +35,8 @@ static inline void fbcon_new_modelist(struct fb_info *info) {}
 static inline void fbcon_get_requirement(struct fb_info *info,
 					 struct fb_blit_caps *caps) {}
 static inline void fbcon_fb_blanked(struct fb_info *info, int blank) {}
+static inline int  fbcon_modechange_possible(struct fb_info *info,
+				struct fb_var_screeninfo *var) { return 0; }
 static inline void fbcon_update_vcs(struct fb_info *info, bool all) {}
 static inline void fbcon_remap_all(struct fb_info *info) {}
 static inline int fbcon_set_con2fb_map_ioctl(void __user *argp) { return 0; }

include/video/of_display_timing.h

@@ -8,6 +8,8 @@
 #ifndef __LINUX_OF_DISPLAY_TIMING_H
 #define __LINUX_OF_DISPLAY_TIMING_H
 
+#include <linux/errno.h>
+
 struct device_node;
 struct display_timing;
 struct display_timings;