linux-kernel - Re: [PATCH 2/2] arm: kprobes: Prohibit kprobes on get

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Message-Id: <20180225212118.ee09db43772a338151762730@kernel.org>
Date:   Sun, 25 Feb 2018 21:21:18 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Wang Nan <wangnan0@...wei.com>,
        Will Deacon <will.deacon@....com>,
        Jon Medhurst <tixy@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        David Long <dave.long@...aro.org>
Subject: Re: [PATCH 2/2] arm: kprobes: Prohibit kprobes on get_user
 functions

On Sat, 24 Feb 2018 17:03:19 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Since do_undefinstr() uses get_user to get the undefined
> instruction, it can be called before kprobes processes
> recursive check. This can cause an infinit recursive
> exception.
> Prohibit probing on get_user functions.
> 
> Fixes: 24ba613c9d6c ("ARM kprobes: core code")
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  arch/arm/include/asm/assembler.h |    8 ++++++++
>  arch/arm/lib/getuser.S           |   10 ++++++++++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
> index bc8d4bbd82e2..dd5e7f30eaed 100644
> --- a/arch/arm/include/asm/assembler.h
> +++ b/arch/arm/include/asm/assembler.h
> @@ -536,4 +536,12 @@ THUMB(	orr	\reg , \reg , #PSR_T_BIT	)
>  #endif
>  	.endm
>  
> +#ifdef CONFIG_KPROBES
> +# define _ASM_NOKPROBE(entry)				\
> +	.pushsection "_kprobe_blacklist", "aw" ;	\
> +	.balign 4 ;					\
> +	.long entry;					\
> +	.popsection

Oops, I missed #else block... which cause build error if !CONFIG_KPROBES.
I'll update it soon.

Thanks,

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