[buildd-tools-devel] Bug#691694: Bug#691694: schroot: /var/lib/schroot/ cannot be a symlink

[Roger Leigh]

On Sun, Oct 28, 2012 at 07:52:24PM +0100, Jakub Wilk wrote:
> An (unintended, I hope) consequence of symlinks mount point
> canonicalisation is that /var/lib/schroot cannot be a symlink
> anymore. In my setup, /var/lib/chroot was a symlink to
> /srv/chroots/meta. This made schroot mount devices in very wrong
> places:
> 
> I: 10mount: /home on /srv/chroots/meta/mount/unstable-i386-2f2404c2-8d99-46a1-b686-8c4f16565f13/srv/chroots/meta/mount/unstable-i386-2f2404c2-8d99-46a1-b686-8c4f16565f13/home type none (rw,bind)

This is indeed unintended, and is due to this logic
from bin/schroot-mount/schroot-mount-main.cc:

  if (directory.size() < opts->mountpoint.size() ||
      directory.substr(0,opts->mountpoint.size()) != opts->mountpoint)
    directory = opts->mountpoint + directory;

We compare the normalised path to the mount directory before
prepending it.  We need to normalise the mount directory as
well to take into account making it a symlink as you have done
here; currently the code makes the (bad) assumption that this
will not contain symlinks.  The solution is just to add a second
realpath(3) call before the comparison to normalise that path
as well.


Regards,
Roger

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