linux-kernel - Re: kernel hangs when kprobe memcpy

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Date:   Tue, 31 Jan 2023 11:38:41 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: kernel hangs when kprobe memcpy



On 01/16/2023 02:41 PM, Masami Hiramatsu (Google) wrote:
> Hi Tiezhu,
>
> On Sat, 14 Jan 2023 14:53:21 +0800
> Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:

...

>>> If you saw that without any change, please report it. At least
>>> memcpy is already marked as noinstr.
>>
>> The current upstream mainline kernel has no problem, because it includes
>> commit e3a9e681adb7 ("x86/entry: Fixup bad_iret vs noinstr"), memcpy is
>> already marked as noinstr. But for the kernel without the above commit,
>> like kernel 5.7, it has problem.
>
> I've confirmed that kernel 5.4.228 (the latest stable tree) did not have
> this issue (it already rejects the memcpy).

I just tested the stable kernel 5.4.230 on x86_64 fedora 36,
without any change, kernel hangs when execute cmd:
modprobe kprobe_example symbol="memcpy"

https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.4.230.tar.xz

Am I missing something? Since 5.4 is a stable tree, should we do 
something to fix it?

Thanks,
Tiezhu