linux-kernel - Re: [PATCH] kprobes/x86: opt: free optinsn cache when range check fails

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Message-ID: <53D6FC38.8070801@hitachi.com>
Date:	Tue, 29 Jul 2014 10:43:20 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <ak@...ux.intel.com>,
	Pei Feiyue <peifeiyue@...wei.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kprobes/x86: opt: free optinsn cache when range check
 fails

(2014/07/28 21:20), Wang Nan wrote:
> This patch frees optinsn slot when range check error to prevent memory
> leaks. Before this patch, cache entry in kprobe_insn_cache won't be
> freed if kprobe optimizing fails due to range check failure.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>

Oops, thank you for finding it!

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

BTW, would you really have hit this error?
I'd like to know the case if this really happens.

> ---
>  arch/x86/kernel/kprobes/opt.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
> index f304773..f1314d0 100644
> --- a/arch/x86/kernel/kprobes/opt.c
> +++ b/arch/x86/kernel/kprobes/opt.c
> @@ -338,8 +338,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
>  	 * a relative jump.
>  	 */
>  	rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
> -	if (abs(rel) > 0x7fffffff)
> +	if (abs(rel) > 0x7fffffff) {
> +		__arch_remove_optimized_kprobe(op, 0);
>  		return -ERANGE;
> +	}
>  
>  	buf = (u8 *)op->optinsn.insn;
>  
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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