Quite a lot of things.  The problem with grsecurity&#x27;s claim that Linux doesn&#x27;t care about security is that grsecurity doesn&#x27;t appear to care about anything <i>but</i> security.  They include changes with significant performance impact, changes that break existing userspace programs, and changes that significantly impact the maintainability of the kernel.  Security that people can&#x27;t or won&#x27;t use doesn&#x27;t actually make people more secure; usability, performance, compatibility, and other such concerns are all part of building a secure system.<p>grsecurity has done a <i>huge</i> amount of innovation in kernel security, and they deserve quite a bit of credit for that.  But grsecurity made a very public and vocal decision to no longer attempt to get any of that work into the upstream kernel, because they don&#x27;t enjoy having to deal with the process involved in <i>collaborative</i> development.  Instead, they went off and built a company around their out-of-tree work, and try to advocate that people use it.<p>Meanwhile, some of the ideas that grsecurity pioneered (and a lot of other security innovations from other sources too) have started to make their way into the kernel, championed by people who <i>are</i> willing to do the work and participate in a collaborative development process.  And the repeated response from grsecurity involves public whining, bashing of people doing the work they refuse to do, and, of course, advertisement.<p>Whining that Linux doesn&#x27;t have the security technology that they do seems rather hollow coming from people who very vocally gave up on doing the work to actually make Linux better.  Out-of-tree, out-of-sight, out-of-mind.