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Message-ID: <CABqD9hY1P7LfmBwQwSG7jDZmw6d_pZH4q2cZq_4ssjQUKRA32w@mail.gmail.com>
Date: Mon, 27 Feb 2012 13:47:17 -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 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? I don't see
these in kernel-next yet and I can't tell if there is a public -mm
anywhere anymore. I can use the patches from the mailing list with
Denys's changes if that'd be good enough. His cleanup will make this
code even smaller!
>> --- 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. (More follow-ups
to your reviews incoming too :).
Thanks!
will
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