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

[James Clarke]

On 6 Mar 2017, at 16:40, Simon McVittie <smcv at debian.org> wrote:
> 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.

This is incredibly similar to what I had stashed from many months back. I even
had some commented-out code involving /dev/console, but it's so long ago that I
can't remember why I wasn't able to get it to work. I've taken my old patch and
improved it with some of your changes, and am currently testing it to ensure it
does actually work properly. Thanks for investigating this; it looks like we
will be able to get this fixed properly!

Thanks,
James

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