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    SubjectRe: [ 020/184] ptrace: ensure arch_ptrace/ptrace_request can never
    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;



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