From: "Dmitry V. Levin" <ldv@altlinux.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Elvira Khabirova <lineprinter@altlinux.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Eugene Syromyatnikov <esyr@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
strace-devel@lists.strace.io, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.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 02:27:53 +0300 [thread overview]
Message-ID: <20181127232753.GA18755@altlinux.org> (raw)
In-Reply-To: <20181127123116.GA13284@redhat.com>
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On Tue, Nov 27, 2018 at 01:31:17PM +0100, Oleg Nesterov wrote:
> On 11/27, Elvira Khabirova wrote:
> > On Mon, 26 Nov 2018 15:35:24 +0100, Oleg Nesterov wrote:
> > > On 11/25, Elvira Khabirova wrote:
> > > >
> > > > Extend PTRACE_GET_SYSCALL_INFO to support PTRACE_EVENT_SECCOMP stops.
> > > > The information returned is the same as for syscall-enter-stops.
> > >
> > > Oh, this is not nice ;) there must be a better option, I hope... Plus
> > >
> > >
> > > Can't ptrace_get_syscall() check
> > >
> > > child->exit_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP;
> > >
> > > to detect the PTRACE_EVENT_SECCOMP case?
> >
> > Nope; looks like exit_code is zeroed after wait().
>
> Yes, thanks for correcting me,
>
> but we can use child->last_siginfo->si_code.
Yes, this approach works, thanks!
> 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, so I'd rather add a comment in the new code.
> And if we require that the user of ptrace_get_syscall() should also use TRACESYSGOOD
> then ptrace_get_syscall() can probably do something like
>
> int entry;
>
> if (!child->last_siginfo)
> return -EINVAL;
> else if (child->last_siginfo->si_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP)
> entry = 1;
> else if (child->last_siginfo->si_code == SIGTRAP | 0x80)
> entry = child->ptrace_message == PTRACE_EVENTMSG_SYSCALL_ENTRY;
> else
> return -EINVAL;
>
> and this way PTRACE_EVENTMSG_SYSCALL_ENTRY/EXIT can't confict with seccomp or
> anything else.
>
> No?
>
> 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.
--
ldv
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next prev parent reply other threads:[~2018-11-27 23:27 UTC|newest]
Thread overview: 18+ 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 1:22 ` [PATCH RESEND v3 1/3] ptrace: pass type of a syscall-stop in ptrace_message Elvira Khabirova
2018-11-25 1:54 ` Joey Pabalinas
2018-11-25 2:10 ` Dmitry V. Levin
2018-11-25 6:17 ` Joey Pabalinas
2018-11-26 14:56 ` Oleg Nesterov
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 ` [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO Elvira Khabirova
2018-11-26 14:35 ` Oleg Nesterov
2018-11-27 3:07 ` Elvira Khabirova
2018-11-27 3:21 ` Dmitry V. Levin
2018-11-27 12:31 ` Oleg Nesterov
2018-11-27 23:27 ` Dmitry V. Levin [this message]
2018-11-28 12:35 ` Oleg Nesterov
2018-11-28 12:44 ` Dmitry V. Levin
2018-11-28 13:13 ` Oleg Nesterov
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