From: u3557@miso.sublimeip.com (Amnon Shiloh)
To: oleg@redhat.com (Oleg Nesterov)
Cc: gorcunov@openvz.org (Cyrill Gorcunov),
xemul@parallels.com (Pavel Emelyanov),
rostedt@goodmis.org (Steven Rostedt),
fweisbec@gmail.com (Frederic Weisbecker),
mingo@redhat.com (Ingo Molnar),
a.p.zijlstra@chello.nl (Peter Zijlstra),
linux-kernel@vger.kernel.org
Subject: Re: arch_check_bp_in_kernelspace: fix the range check
Date: Mon, 26 Nov 2012 10:48:34 +1100 (EST) [thread overview]
Message-ID: <20121125234834.DAC34592076@miso.sublimeip.com> (raw)
In-Reply-To: <20121125225533.GA24905@redhat.com>
Hi Oleg,
> > 2) I was then told (in my own words): "oh, don't worry, the vsyscall page
> > has now been minimized, all it contains now is *real* system calls,
> > and it always calls them".
>
> Not sure where did you get this idea ;) From the very beginning you were
> told that EMULATE mode doesn't do this.
Sorry, I was not aware of the existence of "EMULATE" at the time,
or that it was the default, so I lived in a "NATIVE" world... and
was content that yesterday's problem was solved... I just looked
at the vsyscall page itself, found the system-calls there and was
"happy" with it, that I could now catch them like anywhere else.
> > 8) Any solution that allows a ptracer to prevent its traced process
> > from entering the vsyscall page and execute there system-calls
> > unchecked (thus in effect escape its jailer), would do for me.
>
> Well. I am even more confused... probably this was already discussed
> and I missed this, but.
>
> Why do you need to _prevent_, say, sys_gettimeofday()? Why we can't
> change emulate_vsyscall() to respect PTRACE_SYSCALL and report
> TRAP_VSYSCALL or PTRACE_EVENT_VSYSCALL as I tried to suggest in
> http://marc.info/?l=linux-kernel&m=135343635523715 ?
>
> Oleg.
>
For my own application, I would be happy with this.
But I suspect it might break current versions of "strace",
or similar programs that expect to find the program-counter
pointing at a "syscall" instruction.
At present "strace" fails to report "gettimeofday()", but at
least it does not crash. Surely "strace" can and should be
enhanced to handle this, but existing versions may suffer.
>
> You previously replied that this can not work. Now that you see that
> this _can_ work, could you please explain why this is not enough?
I think it COULD work, but not based on PTRACE_SYSCALL
(or PTRACE_SYSEMU) alone. A new ptrace option will be needed, saying:
"Yes, I am aware of TRAP_VSYSCALL and I know how to handle it."
While for my own application, just fixing the range-check in
arch_check_bp_in_kernelspace will do, requiring a smaller patch,
I agree that fixing this properly by adding a new ptrace option
can help other programmers, so they need not bother with the x86
debug-registers (or perhaps they may need them for other purposes).
Best Regards,
Amnon.
next prev parent reply other threads:[~2012-11-25 23:48 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-09 18:29 [PATCH] arch_check_bp_in_kernelspace: fix the range check Oleg Nesterov
2012-11-09 18:30 ` Oleg Nesterov
2012-11-19 17:47 ` Oleg Nesterov
2012-11-19 18:25 ` Steven Rostedt
2012-11-20 10:33 ` u3557
2012-11-20 15:48 ` Oleg Nesterov
2012-11-20 15:55 ` Steven Rostedt
2012-11-20 18:32 ` Oleg Nesterov
2012-11-20 23:16 ` u3557
2012-11-21 14:16 ` Oleg Nesterov
2012-11-21 17:30 ` Amnon Shiloh
2012-11-22 16:12 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range check) Oleg Nesterov
2012-11-22 20:57 ` Pavel Emelyanov
2012-11-23 0:20 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range Amnon Shiloh
2012-11-23 17:45 ` Oleg Nesterov
2012-11-24 12:47 ` Amnon Shiloh
2012-11-23 17:42 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range check) Oleg Nesterov
2012-11-23 9:14 ` arch_check_bp_in_kernelspace: fix the range check Amnon Shiloh
2012-11-23 16:33 ` Oleg Nesterov
2012-11-23 17:05 ` Oleg Nesterov
2012-11-24 14:14 ` Amnon Shiloh
2012-11-24 13:45 ` Amnon Shiloh
2012-11-25 22:55 ` Oleg Nesterov
2012-11-25 23:48 ` Amnon Shiloh [this message]
2012-12-02 19:30 ` PTRACE_SYSCALL && vsyscall (Was: arch_check_bp_in_kernelspace: fix the range check) Oleg Nesterov
2012-12-02 23:54 ` u3557
2012-12-04 17:59 ` Oleg Nesterov
2012-12-04 22:44 ` u3557
2013-01-08 17:08 ` Pedro Alves
2013-01-09 17:52 ` Oleg Nesterov
2013-01-10 6:54 ` u3557
2013-01-12 18:12 ` Oleg Nesterov
2013-01-14 2:31 ` u3557
2013-01-14 16:01 ` Oleg Nesterov
2013-02-18 1:39 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-18 5:44 ` prctl(PR_SET_MM) Randy Dunlap
2013-02-18 15:21 ` prctl(PR_SET_MM) Steven Rostedt
2013-02-18 16:33 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-18 19:49 ` prctl(PR_SET_MM) Steven Rostedt
2013-02-19 6:25 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-20 8:39 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-20 9:38 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-20 10:51 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-20 11:16 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-21 7:46 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-21 8:00 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-21 8:03 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-21 8:09 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-21 22:18 ` prctl(PR_SET_MM) Andrew Morton
2013-02-21 22:42 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-22 1:18 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-22 14:23 ` prctl(PR_SET_MM) Denys Vlasenko
2012-12-05 9:29 ` PTRACE_SYSCALL && vsyscall (Was: arch_check_bp_in_kernelspace: fix the range check) Jan Kratochvil
2012-12-05 13:14 ` u3557
2012-11-26 9:44 ` vdso && cr " Cyrill Gorcunov
2012-11-26 12:27 ` Andrey Wagin
2012-11-26 12:55 ` Amnon Shiloh
2012-11-26 14:18 ` Cyrill Gorcunov
2012-11-26 14:26 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range Amnon Shiloh
2012-11-26 14:41 ` vdso && cr Cyrill Gorcunov
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