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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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