From: "Dmitry V. Levin" <ldv-u2l5PoMzF/Vg9hUCZPvPmw@public.gmane.org>
To: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Eugene Syromyatnikov
<esyr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
strace-devel-3+4lAyCyj6AWlMsSdNXQLw@public.gmane.org
Subject: Re: [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO
Date: Wed, 28 Nov 2018 15:44:11 +0300 [thread overview]
Message-ID: <20181128124411.GA28206@altlinux.org> (raw)
In-Reply-To: <20181128123545.GA30395-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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On Wed, Nov 28, 2018 at 01:35:46PM +0100, Oleg Nesterov wrote:
> On 11/28, Dmitry V. Levin wrote:
> >
> > > Just like ptrace_request(PTRACE_LISTEN)
> > > does but you can do this lockless (no need to lock_task_sighand()).
> >
> > Why this can be done lockless? All other places in that file do
> > the locking,
>
> PTRACE_LISTEN too doesn't need lock_task_sighand() to access ->last_siginfo,
> this code predates ptrace_freeze_traced() which ensures that the tracee can't
> go away and clear ->last_siginfo.
>
> However, unlike ptrace_get_syscall(), PTRACE_LISTEN needs spin_lock_irq(siglock),
> it modifies ->jobctl and calls signal_wake_up().
What about PTRACE_GETSIGINFO? Can it also be done lockless because
ptrace_check_attach() has already called ptrace_freeze_traced()?
> > > Of course, debugger can do PTRACE_SETSIGINFO and confuse itself but probably we
> > > do not care?
> >
> > The only potential issue I could think of is whether PTRACE_SETSIGINFO
> > could be used this way to cause an information leak by making
> > PTRACE_GET_SYSCALL_INFO access some unrelated data.
>
> Well, afaics ptrace_get_syscall() does nothing "special", debugger can use other
> PTRACE_ requests to get the same info?
I agree.
--
ldv
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WARNING: multiple messages have this Message-ID (diff)
From: "Dmitry V. Levin" <ldv@altlinux.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Elvira Khabirova <lineprinter@altlinux.org>,
Eugene Syromyatnikov <esyr@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
strace-devel@lists.strace.io
Subject: Re: [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO
Date: Wed, 28 Nov 2018 15:44:11 +0300 [thread overview]
Message-ID: <20181128124411.GA28206@altlinux.org> (raw)
In-Reply-To: <20181128123545.GA30395@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 1270 bytes --]
On Wed, Nov 28, 2018 at 01:35:46PM +0100, Oleg Nesterov wrote:
> On 11/28, Dmitry V. Levin wrote:
> >
> > > Just like ptrace_request(PTRACE_LISTEN)
> > > does but you can do this lockless (no need to lock_task_sighand()).
> >
> > Why this can be done lockless? All other places in that file do
> > the locking,
>
> PTRACE_LISTEN too doesn't need lock_task_sighand() to access ->last_siginfo,
> this code predates ptrace_freeze_traced() which ensures that the tracee can't
> go away and clear ->last_siginfo.
>
> However, unlike ptrace_get_syscall(), PTRACE_LISTEN needs spin_lock_irq(siglock),
> it modifies ->jobctl and calls signal_wake_up().
What about PTRACE_GETSIGINFO? Can it also be done lockless because
ptrace_check_attach() has already called ptrace_freeze_traced()?
> > > Of course, debugger can do PTRACE_SETSIGINFO and confuse itself but probably we
> > > do not care?
> >
> > The only potential issue I could think of is whether PTRACE_SETSIGINFO
> > could be used this way to cause an information leak by making
> > PTRACE_GET_SYSCALL_INFO access some unrelated data.
>
> Well, afaics ptrace_get_syscall() does nothing "special", debugger can use other
> PTRACE_ requests to get the same info?
I agree.
--
ldv
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next prev parent reply other threads:[~2018-11-28 12:44 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-25 1:21 [PATCH RESEND v3 0/3] ptrace: add PTRACE_GET_SYSCALL_INFO request Elvira Khabirova
2018-11-25 1:21 ` Elvira Khabirova
2018-11-25 1:22 ` [PATCH RESEND v3 1/3] ptrace: pass type of a syscall-stop in ptrace_message Elvira Khabirova
2018-11-25 1:22 ` Elvira Khabirova
2018-11-25 1:54 ` Joey Pabalinas
[not found] ` <20181125015402.glcaw3kghcu4pr22-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-11-25 2:10 ` Dmitry V. Levin
2018-11-25 2:10 ` Dmitry V. Levin
[not found] ` <20181125021059.GA1190-u2l5PoMzF/Vg9hUCZPvPmw@public.gmane.org>
2018-11-25 6:17 ` Joey Pabalinas
2018-11-25 6:17 ` Joey Pabalinas
2018-11-26 14:56 ` Oleg Nesterov
[not found] ` <20181126145643.GD1660-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-11-27 2:53 ` Elvira Khabirova
2018-11-27 2:53 ` Elvira Khabirova
2018-11-27 3:48 ` Dmitry V. Levin
2018-11-25 1:23 ` [PATCH RESEND v3 2/3] ptrace: add PTRACE_GET_SYSCALL_INFO request Elvira Khabirova
2018-11-25 1:23 ` Elvira Khabirova
2018-11-25 1:23 ` [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO Elvira Khabirova
2018-11-25 1:23 ` Elvira Khabirova
2018-11-26 14:35 ` Oleg Nesterov
2018-11-26 14:35 ` Oleg Nesterov
[not found] ` <20181126143524.GB1660-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-11-27 3:07 ` Elvira Khabirova
2018-11-27 3:07 ` Elvira Khabirova
2018-11-27 3:21 ` Dmitry V. Levin
2018-11-27 3:21 ` Dmitry V. Levin
2018-11-27 12:31 ` Oleg Nesterov
[not found] ` <20181127123116.GA13284-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-11-27 23:27 ` Dmitry V. Levin
2018-11-27 23:27 ` Dmitry V. Levin
2018-11-28 12:35 ` Oleg Nesterov
[not found] ` <20181128123545.GA30395-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-11-28 12:44 ` Dmitry V. Levin [this message]
2018-11-28 12:44 ` Dmitry V. Levin
2018-11-28 13:13 ` Oleg Nesterov
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