Index: wp-includes/js/media-views.js
===================================================================
--- wp-includes/js/media-views.js	(revision 23005)
+++ wp-includes/js/media-views.js	(working copy)
@@ -1776,6 +1776,13 @@
 			if ( ! this.views.attached )
 				this.attach();
 
+			// Attempt to work around a nasty long-standing bug with position: fixed in iOS Safari
+			if ( /Mobile\/.+Safari/.test(window.navigator.userAgent) ) {
+				$('div.media-modal, div.media-modal-backdrop').css('position', 'absolute');
+				// making the modal position: absolute pins it at the top of the window :(
+				$(window).scrollTop(0);
+			}
+
 			this.$el.show().focus();
 			return this.propagate('open');
 		},