Date: Wed, 31 Jan 2018 14:13:45 +0000 From: "Van De Ven, Arjan" <arjan.van.de.ven@...el.com> To: Ingo Molnar <mingo@...nel.org> CC: "Williams, Dan J" <dan.j.williams@...el.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, linux-arch <linux-arch@...r.kernel.org>, Cyril Novikov <cnovikov@...x.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Peter Zijlstra <peterz@...radead.org>, Catalin Marinas <catalin.marinas@....com>, X86 ML <x86@...nel.org>, Will Deacon <will.deacon@....com>, Russell King <linux@...linux.org.uk>, Ingo Molnar <mingo@...hat.com>, Greg KH <gregkh@...uxfoundation.org>, "H. Peter Anvin" <hpa@...or.com>, Alan Cox <alan@...ux.intel.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: RE: [PATCH v5 02/12] array_idx: sanitize speculative array de-references > > short term there was some extremely rudimentary static analysis done. clearly > > that has extreme limitations both in insane rate of false positives, and missing > > cases. > > What was the output roughly, how many suspect places that need > array_idx_nospec() > handling: a few, a few dozen, a few hundred or a few thousand? > > I'm guessing 'static tool emitted hundreds of sites with many false positives > included, but the real sites are probably a few dozen' - but that's really just a > very, very wild guess. your guess is pretty accurate; we ended up with some 15 or so places (the first patch kit Dan mailed out) > > - If it's more than a few dozen then intuitively I'd also be very much in favor of > compiler help: for example trickle down __user annotations that Sparse uses > some > more and let the compiler sanitize indices or warn about them - without hurting > performance of in-kernel array handling. we need this kind of help even if it's only for the static analysis tool > Also, IMHO any tooling should very much be open source: this isn't the kind of > bug > that can be identified via code review, so there's no fall-back detection method > like we have for buffer overflows. we absolutely need some good open source tooling; my personal preference will be a compiler plugin; that way you can use all the fancy logic inside the compilers for analysis, and you can make a "I don't care just fix it" option in addition to flagging for human inspection as the kernel would.
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