Re: [Ksummit-discuss] [CORE TOPIC] Kernel tinification: shrinking the kernel and avoiding size regressions

[Dave Jones <davej@redhat.com>]

On Fri, May 02, 2014 at 09:45:18PM +0100, Ben Hutchings wrote:
 > On Fri, 2014-05-02 at 15:49 -0400, Dave Jones wrote:
 
 > > To use just one example, on certain systems I'd love to be able to just
 > > turn off sys_perf_event_open given what a trainwreck of vulnerabilities it's been
 > > over the last few years [comedy: it is actually a config option, but x86
 > > 'selects' it, so you'll have it and you'll like it].
 > > Thankfully at least the scarier parts of it are now hidden behind the
 > > paranoid sysctl.
 > 
 > I have considered proposing perf_event_paranoid=3 to disable it
 > completely for non-root.

Doesn't seem too crazy an idea to me.

 > > It's this "not used by every user" code that tends to scare me, because
 > > it's written with 1-2 well behaved bits of userspace in mind, which
 > > usually means "has so many unchecked corner cases it's not even funny"
 > [...]
 > 
 > Since Michael often seems to be the one testing those corner cases while
 > writing documentation, it seems like you're getting back to the old
 > issue of whether lack of documentation should be a blocker for adding
 > new system calls.

That, and test cases.

	Dave