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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200828141917.GE1362448@hirez.programming.kicks-ass.net>
Date:   Fri, 28 Aug 2020 16:19:17 +0200
From:   peterz@...radead.org
To:     "Eddy_Wu@...ndmicro.com" <Eddy_Wu@...ndmicro.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.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

On Fri, Aug 28, 2020 at 02:11:18PM +0000, Eddy_Wu@...ndmicro.com wrote:
> > 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

I was under the same impression, we create a brand new stack-frame for
the new task, this 'fake' frame we can schedule into.

It either points to ret_from_fork() for new user tasks, or
kthread_frame_init() for kernel threads.