tty: handle the case where we cannot restore a line discipline
Historically the N_TTY driver could never fail but this has become broken over time. Rather than trying to rewrite half the ldisc layer to fix the breakage introduce a second level of fallback with an N_NULL ldisc which cannot fail, and thus restore the guarantees required by the ldisc layer. We still try and fail to N_TTY first. It's much more useful to find yourself back in your old ldisc (first attempt) or in N_TTY (second attempt), and while I'm not aware of any code out there that makes those assumptions it's good to drive(r) defensively. Signed-off-by:Alan Cox <alan@linux.intel.com> Reported-by:
Dmitry Vyukov <dvyukov@google.com> Tested-by:
Dmitry Vyukov <dvyukov@google.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
47f58e32
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