[PATCH] fbdev: Fix crash if fb_set_var() called before register_framebuffer()

The field info->modelist is initialized during register_framebuffer.  This
field is also referred to in fb_set_var().  Thus a call to fb_set_var()
before register_framebuffer() will cause a crash.  A few drivers do this,
notably controlfb.  (This might fix reports of controlfb crashing in
powermacs).
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/video/fbmem.c

@@ -725,7 +725,10 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 			fb_set_cmap(&info->cmap, info);
 
 			fb_var_to_videomode(&mode, &info->var);
-			fb_add_videomode(&mode, &info->modelist);
+
+			if (info->modelist.prev && info->modelist.next &&
+			    !list_empty(&info->modelist))
+				fb_add_videomode(&mode, &info->modelist);
 
 			if (info->flags & FBINFO_MISC_MODECHANGEUSER) {
 				struct fb_event event;