From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 3/3] arm64: Add seccomp support
Date: Fri, 15 Aug 2014 15:33:46 +0100 [thread overview]
Message-ID: <20140815143346.GV27466@arm.com> (raw)
In-Reply-To: <53E9F7E1.9090405@linaro.org>
On Tue, Aug 12, 2014 at 12:17:53PM +0100, AKASHI Takahiro wrote:
> On 08/12/2014 06:40 PM, Will Deacon wrote:
> > On Tue, Aug 12, 2014 at 07:57:25AM +0100, AKASHI Takahiro wrote:
> >>
> >> > case SECCOMP_MODE_FILTER:
> >> > case SECCOMP_RET_TRACE:
> >> > ...
> >> > if (syscall_get_nr(current, regs) < 0)
> >> > goto skip;
> >>
> >> This implies that we should modify syscallno *before* __secure_computing()
> >> returns.
> >
> > Why does it imply that? There are four competing entities here:
> >
> > - seccomp
> > - tracehook
> > - ftrace (trace_sys_*)
> > - audit
> >
> > With the exception of ftrace, they can all potentially rewrite the pt_regs
> > (the code you cite above is just below a ptrace_event call), so we have
> > to choose some order in which to call them.
>
> (audit won't change registers.)
Sorry, you're quite right.
> > On entry, x86 and arm call them in the order I listed above, so it seems
> > sensible to follow that.
>
> Right, but as far as I understand, ptrace_event() in __secure_computing()
> calls ptrace_notify(), and eventually executes ptrace_stop(), which can
> be stopped while tracer runs (until ptrace(PTRACE_CONT)?).
> So syscall_get_nr() is expected to return -1 if trace changes a syscall number to -1
> (as far as sycall_get_nr() refers to syscallno in pt_regs).
>
> That is why I think we should have PTRACE_SET_SYSCALL.
Gotcha, yeah that looks like the cleanest approach after all. Thanks for the
explanation.
Will
next prev parent reply other threads:[~2014-08-15 14:33 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-22 9:14 [PATCH v5 0/3] arm64: Add seccomp support AKASHI Takahiro
2014-07-22 9:14 ` [PATCH v5 1/3] arm64: ptrace: reload a syscall number after ptrace operations AKASHI Takahiro
2014-07-22 20:15 ` Kees Cook
2014-07-23 7:03 ` AKASHI Takahiro
2014-07-23 8:25 ` Will Deacon
2014-07-23 9:09 ` AKASHI Takahiro
2014-07-23 15:13 ` Kees Cook
2014-07-24 3:54 ` Andy Lutomirski
2014-07-24 5:57 ` AKASHI Takahiro
2014-07-24 15:01 ` Andy Lutomirski
2014-07-25 10:36 ` AKASHI Takahiro
2014-07-25 11:03 ` Will Deacon
2014-07-29 6:49 ` AKASHI Takahiro
2014-07-29 13:26 ` Will Deacon
2014-07-22 9:14 ` [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure computing mode 1 AKASHI Takahiro
2014-07-24 3:40 ` Andy Lutomirski
2014-07-24 4:41 ` Kees Cook
2014-07-24 5:17 ` AKASHI Takahiro
2014-07-24 14:57 ` Andy Lutomirski
2014-07-25 8:52 ` AKASHI Takahiro
2014-07-22 9:14 ` [PATCH v5 3/3] arm64: Add seccomp support AKASHI Takahiro
2014-07-24 3:52 ` Andy Lutomirski
2014-07-24 5:40 ` AKASHI Takahiro
2014-07-24 15:00 ` Andy Lutomirski
2014-07-24 15:16 ` Catalin Marinas
2014-07-25 9:37 ` AKASHI Takahiro
2014-08-05 15:08 ` Kees Cook
2014-08-08 7:35 ` AKASHI Takahiro
2014-08-11 9:24 ` Will Deacon
2014-08-12 6:57 ` AKASHI Takahiro
2014-08-12 9:40 ` Will Deacon
2014-08-12 11:17 ` AKASHI Takahiro
2014-08-15 14:33 ` Will Deacon [this message]
2014-07-22 20:16 ` [PATCH v5 0/3] " Kees Cook
2014-07-23 7:09 ` AKASHI Takahiro
2014-07-23 15:36 ` Kees Cook
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