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

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Message-ID: <CA+55aFzXEoTyK0Sm-y=6xGmLMWzQiSQ7ELJ2-WL_PrP3r44MSg@mail.gmail.com>
Date:	Sun, 3 Jul 2011 11:27:47 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	kernel-hardening@...ts.openwall.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Arnd Bergmann <arnd@...db.de>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC v1] implement SL*B and stack usercopy runtime checks

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
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