On Thu, Sep 01, 2016 at 06:46:13PM +0200, Oleg Nesterov wrote: > On 09/01, Ales Novak wrote: > > > > On ptrace_detach(), the TIF_SYSCALL_TRACE in thread->flags of the tracee > > is not cleared up. This results in the tracehook_report_syscall_* being > > called (though there's no longer a tracer listening to that) upon its > > further syscalls. > > > > Example scenario - attach "strace" to a running process and kill it (the > > strace) with SIGKILL. You'll see that the syscall trace hooks are still > > being called. > > We do not really care, if the tracer dies the tracee can be in the > inconsistent state anyway. > > > --- a/kernel/ptrace.c > > +++ b/kernel/ptrace.c > > @@ -85,6 +85,7 @@ void __ptrace_unlink(struct task_struct *child) > > task_clear_jobctl_pending(child, JOBCTL_TRAP_MASK); > > task_clear_jobctl_trapping(child); > > > > + clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE); > > OK, probably this change makes sense anyway, but then you should > remove another clear_tsk_thread_flag(TIF_SYSCALL_TRACE) in ptrace_detach?
You're right, sorry for not noticing that. Also my changelog was misleading, I've tried to fix that. > > And I'd suggest to move this clear_tsk_thread_flag() up, before > spin_lock(siglock). Otherwise it looks as if we should clear this flag > with ->siglock held. Good point also. > > Oleg. > -- Ales Novak SUSE L3
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