linux-kernel - Re: Kernel stack read with PTRACE_EVENT_EXIT and io

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Message-ID: <55bdad37-187b-e1f5-a359-c5206b20ff4d@gmail.com>
Date:   Wed, 23 Jun 2021 17:26:22 +1200
From:   Michael Schmitz <schmitzmic@...il.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        linux-arch <linux-arch@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>, Oleg Nesterov <oleg@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        alpha <linux-alpha@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Arnd Bergmann <arnd@...nel.org>, Tejun Heo <tj@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Subject: Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads

Hi Eric,

Am 23.06.2021 um 09:48 schrieb Michael Schmitz:
>>
>> The challenging ones are /proc/pid/syscall and seccomp which want to see
>> all of the system call arguments.  I think every architecture always
>> saves the system call arguments unconditionally, so those cases are
>> probably not as interesting.  But they certain look like they could be
>> trouble.
>
> Seccomp hasn't yet been implemented on m68k, though I'm working on that
> with Adrian. The sole secure_computing() call will happen in
> syscall_trace_enter(), so all system call arguments have been saved on
> the stack.
>
> Haven't looked at /proc/pid/syscall yet ...

Not supported at present (no HAVE_ARCH_TRACEHOOK for m68k). And the 
syscall_get_arguments I wrote for seccomp support only copies the first 
five data registers, which are always saved.

Cheers,

	Michael