linux-kernel - Re: [PATCH] seccomp: add ptrace commands for suspend/resume

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Message-ID: <20150603165451.GA20911@redhat.com>
Date:	Wed, 3 Jun 2015 18:54:51 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tycho Andersen <tycho.andersen@...onical.com>
Cc:	Andrey Wagin <avagin@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-api@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>,
	Roland McGrath <roland@...k.frob.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>
Subject: Re: [PATCH] seccomp: add ptrace commands for suspend/resume

On 06/03, Tycho Andersen wrote:
>
> On Tue, Jun 02, 2015 at 08:48:48PM +0200, Oleg Nesterov wrote:
>
> > Otherwise, if we use PTRACE_O_ instead, it goes away automatically if
> > the tracer dies or does PTRACE_DETACH.
>
> IIRC the flag goes away, but we still have to do something in
> __ptrace_unlink to clear the seccomp suspended, so I'm not sure if the
> automatic-ness helps us.

But we do not need seccomp->suspended at all?

Unless I missed something PTRACE_O_ needs a one-liner patch (ignoring
the defines in include files),

--- x/kernel/seccomp.c
+++ x/kernel/seccomp.c
@@ -692,6 +692,9 @@ u32 seccomp_phase1(struct seccomp_data *
 	int this_syscall = sd ? sd->nr :
 		syscall_get_nr(current, task_pt_regs(current));
 
+	if (unlikely(current->ptrace & PT_NAME_OF_THIS_OPTION))
+		return OK;
+
 	switch (mode) {
 	case SECCOMP_MODE_STRICT:
 		__secure_computing_strict(this_syscall);  /* may call do_exit */
	

OK, and the same check in secure_computing_strict().

No?

Oleg.

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