Messages in this thread | | | Date | Fri, 23 Nov 2007 13:23:51 +0300 | From | Alexey Dobriyan <> | Subject | Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach |
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On Thu, Nov 22, 2007 at 07:14:59PM +0300, Oleg Nesterov wrote: > If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops tasklist > and then changes the ->state from TASK_TRACED to TASK_RUNNING. > > This can fool another tracer which attaches to us in between. Change the ->state > under tasklist_lock to ensure that ptrace_check_attach() can't wrongly succeed.
ptrace_check_attach? Both do read_lock -- can run in parallel, so how can it help?
> --- PT/kernel/signal.c~1_ptrace_stop 2007-11-21 21:41:02.000000000 +0300 > +++ PT/kernel/signal.c 2007-11-22 16:59:35.000000000 +0300 > @@ -1628,11 +1628,11 @@ static void ptrace_stop(int exit_code, i > } else { > /* > * By the time we got the lock, our tracer went away. > - * Don't stop here. > + * Don't drop the lock yet, another tracer may come. > */ > - read_unlock(&tasklist_lock); > - set_current_state(TASK_RUNNING); > + __set_current_state(TASK_RUNNING); > current->exit_code = nostop_code; > + read_unlock(&tasklist_lock); > } > > /*
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