[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CABqD9hZ3apFGi+BmX5UNgz=NJUbTigj6acDKG=wu9rrL0wN1Ww@mail.gmail.com>
Date: Tue, 28 Feb 2012 12:34:43 -0600
From: Will Drewry <wad@...omium.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com,
netdev@...r.kernel.org, x86@...nel.org, arnd@...db.de, davem@...emloft.net,
hpa@...or.com, mingo@...hat.com, peterz@...radead.org, rdunlap@...otime.net,
mcgrathr@...omium.org, tglx@...utronix.de, luto@....edu, eparis@...hat.com,
serge.hallyn@...onical.com, djm@...drot.org, scarybeasts@...il.com,
indan@....nu, pmoore@...hat.com, akpm@...ux-foundation.org, corbet@....net,
eric.dumazet@...il.com, markus@...omium.org, coreyb@...ux.vnet.ibm.com,
keescook@...omium.org, Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: [PATCH v11 10/12] ptrace,seccomp: Add PTRACE_SECCOMP support
On Tue, Feb 28, 2012 at 11:04 AM, Will Drewry <wad@...omium.org> wrote:
> On Tue, Feb 28, 2012 at 10:43 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>> On 02/27, Will Drewry wrote:
>>> On Mon, Feb 27, 2012 at 11:54 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>>> > On 02/24, Will Drewry wrote:
>>> >>
>>> >> arch/Kconfig | 1 +
>>> >> include/linux/ptrace.h | 7 +++++--
>>> >> include/linux/seccomp.h | 4 +++-
>>> >> include/linux/tracehook.h | 6 ++++++
>>> >> kernel/ptrace.c | 4 ++++
>>> >> kernel/seccomp.c | 18 ++++++++++++++++++
>>> >
>>> > FYI, this conflicts with the changes -mm tree.
>>> >
>>> > The changes in ptrace.* confict with Denys's
>>> > "ptrace: simplify PTRACE_foo constants and PTRACE_SETOPTIONS code"
>>> >
>>> > The change in tracehook.h conflicts with
>>> > "ptrace: the killed tracee should not enter the syscall"
>>>
>>> What's the best way to reconcile this in this day and age?
>>
>> Of course I'd prefer if you make this change on top of Denys's patch ;)
>>
>> Besides, if you agree with PTRACE_EVENT_SECCOMP/PTRACE_O_SECCOMP you
>> need only one trivial change in ptrace.h.
>
> I think that works quite well :)
>
>>> I don't see
>>> these in kernel-next yet and I can't tell if there is a public -mm
>>> anywhere anymore.
>>
>> Strange... I didn't check, but every patch in
>> http://marc.info/?l=linux-mm-commits has this note:
>>
>> The -mm tree is included into linux-next and is updated
>> there every 3-4 working days
>
> It appears to have been pulled in ~8 hours ago. I'm rebasing to next now.
>
>>> >> --- a/kernel/seccomp.c
>>> >> +++ b/kernel/seccomp.c
>>> >> @@ -354,6 +354,24 @@ int __secure_computing_int(int this_syscall)
>>> >> seccomp_send_sigsys(this_syscall, reason_code);
>>> >> return -1;
>>> >> }
>>> >> + case SECCOMP_RET_TRACE: {
>>> >> + int ret;
>>> >> + struct pt_regs *regs = task_pt_regs(current);
>>> >> + if (!(test_tsk_thread_flag(current, TIF_SYSCALL_TRACE)) ||
>>> >> + !(current->ptrace & PT_TRACE_SECCOMP))
>>> >> + return -1;
>>> >> + /*
>>> >> + * PT_TRACE_SECCOMP and seccomp.trace indicate whether
>>> >> + * tracehook_report_syscall_entry needs to signal the
>>> >> + * tracer. This avoids race conditions in hand off and
>>> >> + * the requirement for TIF_SYSCALL_TRACE ensures that
>>> >> + * we are in the syscall slow path.
>>> >> + */
>>> >> + current->seccomp.trace = 1;
>>> >> + ret = tracehook_report_syscall_entry(regs);
>>> >> + current->seccomp.trace = 0;
>>> >> + return ret;
>>> >
>>> > To be honest, this interface looks a bit strange to me...
>>> >
>>> > Once again, sorry if this was already discussed. But perhaps it would
>>> > be better to introduce PTRACE_EVENT_SECCOMP/PTRACE_O_SECCOMP instead?
>>> >
>>> > SECCOMP_RET_TRACE: could simply do ptrace_event(PTRACE_EVENT_SECCOMP)
>>> > unconditionaly. The tracer can set the option and do PTRACE_CONT if it
>>> > doesn't want the system call notifications.
>>>
>>> Works for me - this also gets rid of the extra int for brief state
>>> tracking. I'll switch over to that in the next rev.
>>
>> Great. In this case this patch becomes really trivial. Just 2 defines
>> in ptrace.h and the unconditional ptrace_event() under SECCOMP_RET_TRACE.
hrm the only snag is that I can't then rely on TIF_SYSCALL_TRACE to
ensure seccomp is in the slow-path. Right now, on x86, seccomp is
slow-path, but it doesn't have to be to have the syscall and args.
However, for ptrace to behavior properly, I believed it did need to be
in the slow path. If SECCOMP_RET_TRACE doesn't rely on
PTRACE_SYSCALL, then it introduces a need for seccomp to always be in
the slow path or to flag (somehow) when it needs slow path.
Any suggestions there?
Thanks!
will
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
