linux-kernel - RE: [RFC][PATCH 3/7] kprobes: Remove kretprobe hash

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Date:   Fri, 28 Aug 2020 14:11:18 +0000
From:   "Eddy_Wu@...ndmicro.com" <Eddy_Wu@...ndmicro.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
CC:     "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "naveen.n.rao@...ux.ibm.com" <naveen.n.rao@...ux.ibm.com>,
        "anil.s.keshavamurthy@...el.com" <anil.s.keshavamurthy@...el.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "cameron@...dycamel.com" <cameron@...dycamel.com>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "will@...nel.org" <will@...nel.org>,
        "paulmck@...nel.org" <paulmck@...nel.org>
Subject: RE: [RFC][PATCH 3/7] kprobes: Remove kretprobe hash

> From: Masami Hiramatsu <mhiramat@...nel.org>
>
> OK, schedule function will be the key. I guess the senario is..
>
> 1) kretporbe replace the return address with kretprobe_trampoline on task1's kernel stack
> 2) the task1 forks task2 before returning to the kretprobe_trampoline
> 3) while copying the process with the kernel stack, task2->kretprobe_instances.first = NULL

I think new process created by fork/clone uses a brand new kernel stack? I thought only user stack are copied.
Otherwise any process launch should crash in the same way

By the way, I can reproduce this on the latest branch(v4)
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