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SubjectRe: [PATCH] wait_for_helper: SIGCHLD from user-space can lead to use-after-free
SIGCHLD being blocked doesn't affect reaping, so SIG_IGN or sa_flags &
SA_NOCLDWAIT is the only thing that would do this. How does that come
about here in this kthread? Is it inherited from the instigating user
process? If so, then SA_NOCLDWAIT is as much a problem as SIG_IGN.
Or I guess maybe it's from ignore_signals() in kthreadd()?
In that case SIG_IGN is indeed all that matters. (I don't really
know all the kthread/kmod/userhelper code organization.)

Perhaps it would be cleaner to do:

flush_signal_handlers(current, 1);

in wait_for_helper. That should make it redundant in ____call_usermodehelper,
so it could be removed from there.


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