[kernel-hardening] Re: [RFC v1] implement SL*B and stack usercopy runtime checks

Linus Torvalds
2011-07-03T18:27:47Z

That patch is entirely insane. No way in hell will that ever get merged.

copy_to/from_user() is some of the most performance-critical code, and
runs a *lot*, often for fairly small structures (ie 'fstat()' etc).

Adding random ad-hoc tests to it is entirely inappropriate. Doing so
unconditionally is insane.

So NAK, NAK, NAK.

If you seriously clean it up (that at a minimum includes things like
making it configurable using some pretty helper function that just
compiles away for all the normal cases, and not writing out

if (!slab_access_ok(to, n) || !stack_access_ok(to, n))

multiple times, for chrissake) it _might_ be acceptable.

But in its current form it's just total crap. It's exactly the kind of
"crazy security people who don't care about anything BUT security"
crap that I refuse to see.

Some balance and sanity.

Linus