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From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	tcharding <me@tobin.cc>
Subject: Re: Hashed pointer issues
Date: Mon, 30 Apr 2018 12:41:35 -0400
Message-ID: <20180430124135.0cce92e3@gandalf.local.home> (raw)
In-Reply-To: <CA+55aFwieC1-nAs+NFq9RTwaR8ef9hWa4MjNBWL41F-8wM49eA@mail.gmail.com>

On Mon, 30 Apr 2018 16:31:52 +0000
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, Apr 30, 2018 at 9:11 AM Kees Cook <keescook@chromium.org> wrote:
> 
> > I (or other folks?) had proposed this before, but, AIUI, Linus remains
> > opposed.  
> 
> Yeah, I hate this, because it will make people paper over their problems by
> just booting with that option.
> 
> I think it should just be fixed.
> 
> Is there really any reason why trace buffers have to be dumped so early
> that the entropy hasn't even taken yet?

In this case, an RCU stall was triggering and a "dump on oops" would
dump the trace buffers, (before entropy was established).

> 
> And if we really want a command line option, can we make that still hash
> the pointer, just force the entropy early. That way kernel developers that
> test that command line option are still testing the *hashing*, they just
> are missing the good entropy.
> 

That may work too. Even with bad entropy, pointers at start up are hard
to come by, and I can't see a hacker being able to use them as it only
happens once during boot.

-- Steve

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-30 15:50 Anna-Maria Gleixner
2018-04-30 16:11 ` Kees Cook
2018-04-30 16:31   ` Linus Torvalds
2018-04-30 16:41     ` Steven Rostedt [this message]
2018-04-30 16:57       ` Linus Torvalds
2018-04-30 17:01         ` Linus Torvalds
2018-04-30 17:06           ` Randy Dunlap
2018-04-30 17:12             ` Linus Torvalds
2018-05-01  7:05               ` tcharding
2018-05-03  8:41             ` Geert Uytterhoeven
2018-04-30 18:38           ` Kees Cook
2018-04-30 19:00             ` Linus Torvalds
2018-04-30 19:16               ` Kees Cook
2018-04-30 20:01                 ` Linus Torvalds
2018-04-30 20:07                   ` Linus Torvalds
2018-04-30 21:23                 ` Tobin C. Harding

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