linux-kernel - Re: [RFC PATCH tip/master V3 0/8] kprobes/x86: Make kprobes instruction buffers read-only

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Message-Id: <20170411144413.7f04cf0ec89de1d3362d8dca@kernel.org>
Date:   Tue, 11 Apr 2017 14:44:13 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ye Xiaolong <xiaolong.ye@...el.com>
Subject: Re: [RFC PATCH tip/master V3 0/8] kprobes/x86: Make kprobes
 instruction buffers read-only

Ping?

On Wed, 29 Mar 2017 13:55:44 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Hi,
> 
> This is the 3rd version of the series. I just updated 4/8 according
> to Ingo's comment.
> 
> This series tries to make kprobes instruction buffers read-only
> pages. Since those buffers are used for trampoline code, those
> are a part of "text area" and it should be marked as ro for
> avoiding unexpected modification. And this actually fix a warning
> rodata sanity check reported by lkp-robot.
> 
> https://lkml.org/lkml/2017/2/27/161
> 
> This change requires changing the kprobe-booster at first
> because it can modify the instruction buffer to add a jump while
> resuming from single-stepping. Of course after we make the buffer
> readonly, we may not be able to modify it while probing.
> 
> So, at first this series checks the current bootable instructions
> and fixes a missed instruction (call far), modifies can_boost to
> use x86 instruction decoder, and inserts "booster" jump while
> preparing instruction buffer instead of resuming from single-stepping.
> At last, it makes the buffers for kprobes and optprobe readonly.
> 
> This series also has some cleanup patches related to above 
> changes.
> 
> Changes from V2:
>  - [4/8]: Fix imbalanced curly braces and remove unneeded
>    (void *) cast.
> 
> ---
> 
> Masami Hiramatsu (8):
>       kprobes/x86: Fix not to boost call far instruction
>       kprobes/x86: Fix the description of __copy_instruction()
>       kprobes/x86: Use instruction decoder for booster
>       kprobes/x86: Do not modify singlestep buffer while resuming
>       kprobes/x86: Make boostable flag boolean
>       kprobes/x86: Set kprobes pages readonly
>       kprobes/x86: Use probe_kernel_read instead of memcpy
>       kprobes/x86: Consolidate insn decoder users for copying code
> 
> 
>  arch/x86/include/asm/kprobes.h   |    7 +-
>  arch/x86/kernel/kprobes/common.h |    4 +
>  arch/x86/kernel/kprobes/core.c   |  149 +++++++++++++++++++-------------------
>  arch/x86/kernel/kprobes/ftrace.c |    2 -
>  arch/x86/kernel/kprobes/opt.c    |   13 +++
>  5 files changed, 90 insertions(+), 85 deletions(-)
> 
> --
> Masami Hiramatsu (Linaro) <mhiramat@...nel.org>


-- 
Masami Hiramatsu <mhiramat@...nel.org>