Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Sat, 8 Apr 2017 00:12:53 -0400
From: Daniel Micay <>
To: Kees Cook <>
Cc: Thomas Gleixner <>, Andy Lutomirski <>, 
	Mathias Krause <>, 
	"" <>, Mark Rutland <>, 
	Hoeun Ryu <>, PaX Team <>, 
	Emese Revfy <>, Russell King <>, X86 ML <>, 
	"" <>, 
	"" <>, 
	Peter Zijlstra <>
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.

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.