fbcon: check if the character count can be handled

Fontmaps can be 256 or 512 in length. The only driver that can do tileblitting
can only handle 256 characters.  Check for this when setting the font.
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/console/fbcon.c

@@ -685,6 +685,17 @@ static void set_blitting_type(struct vc_data *vc, struct fb_info *info)
 		fbcon_set_bitops(ops);
 	}
 }
+
+static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
+{
+	int err = 0;
+
+	if (info->flags & FBINFO_MISC_TILEBLITTING &&
+	    info->tileops->fb_get_tilemax(info) < charcount)
+		err = 1;
+
+	return err;
+}
 #else
 static void set_blitting_type(struct vc_data *vc, struct fb_info *info)
 {
@@ -695,6 +706,12 @@ static void set_blitting_type(struct vc_data *vc, struct fb_info *info)
 	fbcon_set_rotation(info);
 	fbcon_set_bitops(ops);
 }
+
+static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
+{
+	return 0;
+}
+
 #endif /* CONFIG_MISC_TILEBLITTING */
 
 
@@ -2518,6 +2535,10 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font, unsigne
 	    !(info->pixmap.blit_y & (1 << (font->height - 1))))
 		return -EINVAL;
 
+	/* Make sure driver can handle the font length */
+	if (fbcon_invalid_charcount(info, charcount))
+		return -EINVAL;
+
 	size = h * pitch * charcount;
 
 	new_data = kmalloc(FONT_EXTRA_WORDS * sizeof(int) + size, GFP_USER);