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SubjectRe: [PATCH 4/4] Allow unprivileged chroot when safe
On Mon, Jan 16, 2012 at 12:15:09PM -0800, Andy Lutomirski wrote:

> The first approach I tried was (from memory -- may not compile at all
> on any version) fs->root.mnt != fs->root.mnt->mnt_parent. That didn't
> work. The issue is that on dracut-based distros, AFAICT, the root (in
> the sense of the root of the tree of struct vfsmounts) is rootfs. The
> apparent root (the filesystem containing /, /usr, etc) is mounted on
> top of (rootfs)/. Dracut then does something with the effect of
> chroot("/"). So you end up with the vfsmount that contains "/" not
> being the actual root vfsmount. But there's nothing hidden by the
> chroot -- even if fs->root.mnt pointed at rootfs, "/" would still
> follow the mountpoint into the actual filesystem.

That has nothing whatsoever to do with dracut. _Everything_ ends up
that way; IOW, everything including init(8) runs chrooted into the
final userland root. On any normal distro. Your test is complete BS - e.g.
mount /dev/crap /mnt/blah
mount /dev/garbage /mnt/blah
chroot /mnt/blah
will *NOT* be chrooted per your definition.


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