Date: Sat, 8 Apr 2017 00:12:53 -0400 From: Daniel Micay <danielmicay@...il.com> To: Kees Cook <keescook@...omium.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Andy Lutomirski <luto@...nel.org>, Mathias Krause <minipli@...glemail.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Mark Rutland <mark.rutland@....com>, Hoeun Ryu <hoeun.ryu@...il.com>, PaX Team <pageexec@...email.hu>, Emese Revfy <re.emese@...il.com>, Russell King <linux@...linux.org.uk>, X86 ML <x86@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Peter Zijlstra <peterz@...radead.org> Subject: Re: Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() > I probably chose the wrong name for this feature (write rarely). > That's _usually_ true, but "sensitive_write()" was getting rather > long. The things that we need to protect with this are certainly stuff > that doesn't get much writing, but some things are just plain > sensitive (like page tables) and we should still try to be as fast as > possible with them. Not too late to rename it. Scoped write? I think it makes change to use a different API than PaX for portability too, but not a different x86 implementation. It's quite important to limit the writes to the calling thread and it needs to perform well to be introduced widely. > I'm all for a general case for the infrastructure (as Andy and Mark > has mentioned), but I don't want to get into the situation where > people start refusing to use it because it's "too slow" (for example, > see refcount_t vs net-dev right now). Meanwhile, the PaX implementation has improved to avoid the issues that were brought up while only introducing a single always-predicted (due to code placement) branch on the overflow flag. That seems to have gone unnoticed upstream, where there's now a much slower implementation that's not more secure, and is blocked from introduction in areas where it's most needed based on the performance. Not to mention that it's opt-in... which is never going to work.
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