Hi Oleg,
On Wed, Jun 05, 2013 at 05:49:51PM +0200, Oleg Nesterov wrote:
> On 06/05, Oleg Nesterov wrote:
> >
> > Note: I can make a _much_ simpler patch for 2.6.32, please let me know
> > if you need it.
> >
> > We can rely on sys_ptrace()->lock_kernel() and simply do lock/unlock
> > if fatal_signal_pending() in ptrace_stop/do_signal_stop. This is not
> > the same, this doesn't prevent wakeup(), but this should be enough.
>
> Something like below. Untested/uncompiled. I think it should close the
> security problems.
>
> Oleg.
>
>
> --- x/kernel/signal.c
> +++ x/kernel/signal.c
> @@ -1545,6 +1545,14 @@ static int sigkill_pending(struct task_s
> sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
> }
>
> +static void ptrace_sync(void)
> +{
> + if (fatal_signal_pending(current)) {
> + lock_kernel();
> + unlock_kernel();
> + }
> +}
> +
> /*
> * This must be called with current->sighand->siglock held.
> *
> @@ -1603,6 +1611,7 @@ static void ptrace_stop(int exit_code, i
> read_unlock(&tasklist_lock);
> preempt_enable_no_resched();
> schedule();
> + ptrace_sync();
> } else {
> /*
> * By the time we got the lock, our tracer went away.
> @@ -1722,6 +1731,9 @@ static int do_signal_stop(int signr)
> schedule();
> } while (try_to_freeze());
>
> + if (current->ptrace)
> + ptrace_sync();
> +
> tracehook_finish_jctl();
> current->exit_code = 0;
>
While I'm unable to tell whether the patch fixes the issue, I totally
trust you on this. So if you have the time to propose a tested patch
(or suggest me how to reliably test it), I'd gladly apply it instead.
Thanks!
Willy
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