Bug#841935: pbuilder: incorrect permissions on /dev/ptmx breaks openpty()

[Simon McVittie]

On Mon, 06 Mar 2017 at 15:30:04 +0000, Thorsten Glaser wrote:
> Simon McVittie dixit:
> >I'm surprised by this. I would have expected that interactive use of
> >tty things inside pbuilder would have started failing when you upgraded
> >to a v4.7+ kernel, because the /dev/pts inside the chroot would no longer
> >be able to "see" the terminal that is on pbuilder's stdin.
> 
> Interestingly enough, the shell does still work. According to
> strace, this is because /dev/tty is still operable.

Right - none of my tests resulted in a completely unusable shell, but they
did have a shell with degraded functionality.

script wants to create ptys, so it suffers from #817236; sudo wants to
communicate with the "parent" terminal, so it suffers from the newinstance
issue that we're now discussing; screen wants both, so it makes a nice
test-case.

    S