linux-kernel - [PATCH RFC 0/5] uprobes: kill xol vma

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Date:	Mon, 28 Nov 2011 20:06:14 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...k.frob.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Stephen Wilson <wilsons@...rt.ca>
Subject: [PATCH RFC 0/5] uprobes: kill xol vma

Hello.

On top of this series, not for inclusion yet, just to explain what
I mean. May be someone can test it ;)

This series kills xol_vma. Instead we use the per_cpu-like xol slots.

This is much more simple and efficient. And this of course solves
many problems we currently have with xol_vma.

For example, we simply can not trust it. We do not know what actually
we are going to execute in UTASK_SSTEP mode. An application can unmap
this area and then do mmap(PROT_EXEC|PROT_WRITE, MAP_FIXED) to fool
uprobes.

The only disadvantage is that this adds a bit more arch-dependant
code.

The main question, can this work? I know very little in this area.
And I am not sure if this can be ported to other architectures.

Please comment.

Oleg.

 arch/x86/include/asm/fixmap.h      |    9 +
 arch/x86/include/asm/thread_info.h |    4 
 arch/x86/kernel/process.c          |    6 
 arch/x86/kernel/uprobes.c          |   26 +++-
 include/linux/mm_types.h           |    1 
 include/linux/uprobes.h            |   27 ----
 kernel/fork.c                      |    2 
 kernel/uprobes.c                   |  239 +++----------------------------------
 8 files changed, 71 insertions(+), 243 deletions(-)

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