Messages in this thread | | | Date | Fri, 23 Nov 2007 13:54:57 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach |
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On 11/23, Alexey Dobriyan wrote: > > 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,
Yep.
> so how can it help?
read_lock prevents ptrace_attach(), so the new tracer can't attach and then do ptrace_check_attach().
Oleg.
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