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Date: Sun, 29 Nov 2015 09:05:05 +0100
From: Ingo Molnar <>
To: Andy Lutomirski <>
Cc: Kees Cook <>,
	Linus Torvalds <>,
	PaX Team <>,
	"" <>,
	Mathias Krause <>,
	"" <>,
	Ingo Molnar <>,
	Thomas Gleixner <>,
	"H. Peter Anvin" <>, x86-ml <>,
	Arnd Bergmann <>,
	Michael Ellerman <>,
	linux-arch <>,
	Emese Revfy <>
Subject: Re: [PATCH 0/2] introduce post-init read-only

* Andy Lutomirski <> wrote:

> >>  - print a warning and a backtrace, and just mark the page read-write
> >> so that the machine survives, but we get notified and can fix whatever
> >> broken code
> >
> > This seems very easy to add. Should I basically reverse the effects of 
> > mark_rodata_ro(), or should I only make the new ro-after-init section as RW? 
> > (I think the former would be easier.)
> I'd suggest verifying that the page in question is .data..ro_after_init and, if 
> so, marking that one page RW.

Yes, this was PaX's suggestion as well, and I agree: doing that turns a quite 
possibly unrecoverable boot/shutdown time or suspend/resume time (suspend is 
really a special category of 'bootup') crasher oops into a more informative stack 

These ro related faults tend to trigger when init/deinit is running, and oopsing 
in those sequences is typically a lot less survivable than say oopsing in a high 
level system call while not holding locks.



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