title: Rooted but su says "Permission denied"
body: <p>I have this "old" Lenovo A2107 tablet which I rooted years ago (using a download from <a href="http://androidforums.com/threads/a2107-root-mods-and-rom-discussion.661261/" rel="noreferrer">http://androidforums.com/threads/a2107-root-mods-and-rom-discussion.661261/</a>, tho running its root.bat script by hand from my GNU/Linux machine) and that worked fine.</p>
  
  <p>Then I passed this tablet to my daughter for a couple years, and now I got it back.</p>
  
  <p>/system/bin/su is still present, still the same date and size, still mode "rwsr-sr-x", still the same firmware (Android 4.0.3) so all looks fine, but when I try to run it from a shell, it just tells me "Permission denied".</p>
  
  <p>Any idea what might be going on?  What I could try to do to track it down?</p>