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SubjectRe: [PATCH] kretprobe: avoid re-registration of the same kretprobe earlier
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Hi steve, Masami,

Thanks for your works, i will check code again and modify properly
according to steve's suggestion.

-- ShaoBo

在 2020/12/2 7:32, Masami Hiramatsu 写道:
> On Mon, 30 Nov 2020 16:18:50 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> Masami,
>>
>> Can you review this patch, and also, should this go to -rc and stable?
>>
>> -- Steve
> Thanks for ping me!
>
>> On Tue, 24 Nov 2020 19:57:19 +0800
>> Wang ShaoBo <bobo.shaobowang@huawei.com> wrote:
>>
>>> Our system encountered a re-init error when re-registering same kretprobe,
>>> where the kretprobe_instance in rp->free_instances is illegally accessed
>>> after re-init.
> Ah, OK. Anyway if re-register happens on kretprobe, it must lose instances
> on the list before checking re-register in register_kprobe().
> So the idea looks good to me.
>
>
>>> Implementation to avoid re-registration has been introduced for kprobe
>>> before, but lags for register_kretprobe(). We must check if kprobe has
>>> been re-registered before re-initializing kretprobe, otherwise it will
>>> destroy the data struct of kretprobe registered, which can lead to memory
>>> leak, system crash, also some unexpected behaviors.
>>>
>>> we use check_kprobe_rereg() to check if kprobe has been re-registered
>>> before calling register_kretprobe(), for giving a warning message and
>>> terminate registration process.
>>>
>>> Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
>>> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
>>> ---
>>> kernel/kprobes.c | 8 ++++++++
>>> 1 file changed, 8 insertions(+)
>>>
>>> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
>>> index 41fdbb7953c6..7f54a70136f3 100644
>>> --- a/kernel/kprobes.c
>>> +++ b/kernel/kprobes.c
>>> @@ -2117,6 +2117,14 @@ int register_kretprobe(struct kretprobe *rp)
>>> }
>>> }
>>>
>>> + /*
>>> + * Return error if it's being re-registered,
>>> + * also give a warning message to the developer.
>>> + */
>>> + ret = check_kprobe_rereg(&rp->kp);
>>> + if (WARN_ON(ret))
>>> + return ret;
> If you call this here, you must make sure kprobe_addr() is called on rp->kp.
> But if kretprobe_blacklist_size == 0, kprobe_addr() is not called before
> this check. So it should be in between kprobe_on_func_entry() and
> kretprobe_blacklist_size check, like this
>
> if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
> return -EINVAL;
>
> addr = kprobe_addr(&rp->kp);
> if (IS_ERR(addr))
> return PTR_ERR(addr);
> rp->kp.addr = addr;
>
> ret = check_kprobe_rereg(&rp->kp);
> if (WARN_ON(ret))
> return ret;
>
> if (kretprobe_blacklist_size) {
> for (i = 0; > > + ret = check_kprobe_rereg(&rp->kp);
>
>
> Thank you,
>
>

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