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Message-ID: <CALCETrXQY3PvLaZXQgN1bw5s7JP6LZSZzChRziFenAiQWA3XpQ@mail.gmail.com>
Date: Fri, 28 Aug 2015 12:22:39 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Chris Metcalf <cmetcalf@...hip.com>
Cc: Gilad Ben Yossef <giladb@...hip.com>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Christoph Lameter <cl@...ux.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 4/6] task_isolation: provide strict mode configurable signal
On Tue, Aug 25, 2015 at 12:55 PM, Chris Metcalf <cmetcalf@...hip.com> wrote:
> Allow userspace to override the default SIGKILL delivered
> when a task_isolation process in STRICT mode does a syscall
> or otherwise synchronously enters the kernel.
>
> In addition to being able to set the signal, we now also
> pass whether or not the interruption was from a syscall in
> the si_code field of the siginfo.
>
> Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
> ---
> include/uapi/linux/prctl.h | 2 ++
> kernel/isolation.c | 17 +++++++++++++----
> 2 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
> index e16e13911e8a..2a4ddc890e22 100644
> --- a/include/uapi/linux/prctl.h
> +++ b/include/uapi/linux/prctl.h
> @@ -195,5 +195,7 @@ struct prctl_mm_map {
> #define PR_GET_TASK_ISOLATION 48
> # define PR_TASK_ISOLATION_ENABLE (1 << 0)
> # define PR_TASK_ISOLATION_STRICT (1 << 1)
> +# define PR_TASK_ISOLATION_SET_SIG(sig) (((sig) & 0x7f) << 8)
> +# define PR_TASK_ISOLATION_GET_SIG(bits) (((bits) >> 8) & 0x7f)
>
> #endif /* _LINUX_PRCTL_H */
> diff --git a/kernel/isolation.c b/kernel/isolation.c
> index a89a6e9adfb4..b776aa632c8f 100644
> --- a/kernel/isolation.c
> +++ b/kernel/isolation.c
> @@ -75,11 +75,20 @@ void task_isolation_enter(void)
> }
> }
>
> -static void kill_task_isolation_strict_task(void)
> +static void kill_task_isolation_strict_task(int is_syscall)
> {
> + siginfo_t info = {};
> + int sig;
> +
> dump_stack();
> current->task_isolation_flags &= ~PR_TASK_ISOLATION_ENABLE;
> - send_sig(SIGKILL, current, 1);
> +
> + sig = PR_TASK_ISOLATION_GET_SIG(current->task_isolation_flags);
> + if (sig == 0)
> + sig = SIGKILL;
> + info.si_signo = sig;
> + info.si_code = is_syscall;
> + send_sig_info(sig, &info, current);
The stuff you're doing here is sufficiently nasty that I think you
should add something like:
rcu_lockdep_assert(rcu_is_watching(), "some message here");
Because as it stands this is just asking for trouble.
For the record, I am *extremely* unhappy with the state of the context
tracking hooks.
--Andy
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