Messages in this thread | | | Date | Thu, 11 Feb 2010 19:55:30 +0100 | From | Oleg Nesterov <> | Subject | Re: Race in ptrace. |
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On 02/11, Salman Qazi wrote: > > >> > // the tracee is STOPPED as requested, not TRACED, > >> > // SIGCONT wakes it up > >> > kill(pid, SIGCONT); > > I am still missing something. There's probably a gap in my > understanding, so let's try to clarify it. The last "kill" call, > sends a SIGCONT. But, shouldn't this SIGCONT be intercepted by the > tracer before the tracee sees it?
No. The tracee resumes (again: because it was STOPPED, not TRACED), dequeues SIGCONT, reports the signal and stops in TASK_TRACED, see ptrace_signal(). Meanwhile, until it calls ptrace_stop(), it is TASK_RUNNING and ptrace() fails.
Oleg.
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