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

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Date:	Wed, 27 Aug 2014 22:37:12 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Wang Nan <wangnan0@...wei.com>, Ingo Molnar <mingo@...hat.com>
Cc:	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


Hi Ingo,

Could you pull this for a bugfix of a memory leak?

(2014/08/27 21:15), Wang Nan wrote:
> On 2014/7/29 9:43, Masami Hiramatsu wrote:
>> (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>
>>
> 
> Hi Masami Hiramatsu,
> 
> I don't find this patch in newest upstream. Is there any problem?
> 
>> 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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