Date: Wed, 2 Oct 2013 07:07:14 +0200 From: Ingo Molnar <mingo@...nel.org> To: Kees Cook <keescook@...omium.org> Cc: linux-kernel@...r.kernel.org, x86@...nel.org, kernel-hardening@...ts.openwall.com, adurbin@...gle.com, Eric Northup <digitaleric@...gle.com>, jln@...gle.com, wad@...gle.com, Mathias Krause <minipli@...glemail.com>, Zhang Yanfei <zhangyanfei@...fujitsu.com>, "H. Peter Anvin" <hpa@...or.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Arnaldo Carvalho de Melo <acme@...radead.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH v6 0/7] Kernel base address randomization * Kees Cook <keescook@...omium.org> wrote: > Here is the latest version of the kASLR series. It has much improved > e820 walking code, and expands the window available on 64-bit. > > This is rolled out on Chrome OS devices, and working well. There's one kernel debuggability detail that should be discussed I think: should symbolic printouts (in oops messages but also in /proc/kallsyms) and instrumentation interfaces that expose kernel addresses attempt to de-randomize the addresses, stack contents and register values that lie within the random range? - it would be easier to use those addresses and look them up in a vmlinux or in a System.map as well. - it would be somewhat safer to post an oops publicly if it did not contain the random offset in an easily identifiable way. - oops patterns from distribution kernels that enable randomization would match up better. - this would make it safer to expose /proc/kallsyms to user-space profiling, while keeping the random offset a kernel-internal secret. - RIP information in profiling streams would thus not contain the kernel random offset either. The other approach would be what your series does, to keep all the raw, randomized output and to assume that users who are allowed to access to logs or profiling can learn the random offset. I tend to lean towards the 'raw' approach that you picked, but an argument can be made for both approaches - and in any case I haven't seen this discussed to conclusion with cons/pros listed and a consensus/decision reached. Thanks, Ingo
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