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Message-ID: <a11a31b6-bff3-b6c1-db47-787540cd0d07@huawei.com>
Date: Thu, 26 Oct 2017 09:22:23 +0800
From: chenjiankang <chenjiankang1@...wei.com>
To: Masami Hiramatsu <mhiramat@...nel.org>
CC: <ananth@...ux.vnet.ibm.com>, <anil.s.keshavamurthy@...el.com>,
<linux-kernel@...r.kernel.org>, <xieyisheng1@...wei.com>,
<wangkefeng.wang@...wei.com>, <davem@...emloft.net>
Subject: Re: [PATCH] kernel/kprobes: add check to avoid kprobe memory leak
> On Tue, 24 Oct 2017 20:17:02 +0800
> JianKang Chen <chenjiankang1@...wei.com> wrote:
>
>> The function register_kretprobe is used to initialize a struct
>> kretprobe and allocate a list table for kprobe instance.
>> However,in this function, there is a memory leak.
>>
>> The test case:
>>
>> static struct kretprobe rp;
>> struct kretprobe *rps[10]={&rp ,&rp ,&rp ,
>> &rp ,&rp ,&rp ,&rp ,&rp ,&rp,&rp};
>
> What ? this is buggy code. you must not list same kretprobe.
> But, year, since register_kprobe() already has similar protection against
> reusing, register_kretprobe() should do so.
>
> [..]
>> raw_spin_lock_init(&rp->lock);
>> +
>> + if (!hlist_empty(&rp->free_instances))
>> + return -EBUSY;
>> +
>
> Hmm, but can you use check_kprobe_rereg() before raw_spin_lock_init()?
> If user reuses rp after it starts, rp->lock can already be used.
Hmm, your advice is very good, we can use check_kprobe_rereg() at
the beginning of the register_kretprobe();
For example:
int register_kretprobe(struct kretprobe *rp)
{
int ret = 0;
struct kretprobe_instance *inst;
int i;
void *addr;
ret = check_kprobe_rereg(&rp->kp);
if (ret)
return ret;
Thank you!
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