Re: [PATCH RFC 0/1] mount: universally disallow mounting over symlinks

Ian Kent
2020-01-13T06:11:04Z

On Mon, 2020-01-13 at 14:00 +0800, Ian Kent wrote:
> On Mon, 2020-01-13 at 03:54 +0000, Al Viro wrote:
> > On Mon, Jan 13, 2020 at 09:48:23AM +0800, Ian Kent wrote:
> >
> > > I did try this patch and I was trying to work out why it didn't
> > > work. But thought I'd let you know what I saw.
> > >
> > > Applying it to current Linus tree systemd stops at switch root.
> > >
> > > Not sure what causes that, I couldn't see any reason for it.
> >
> > Wait a minute... So you are seeing problems early in the boot,
> > before any autofs ioctls might come into play?
>
> I did, then I checked it booted without the patch, then tried
> building from scratch with the patch twice and same thing
> happened each time.
>
> Looked like this, such as it is:
> [ OK ] Reached target Switch Root.
> [ OK ] Started Plymouth switch root service.
> Starting Switch Root...
>
> I don't have any evidence but thought it might be this:
> https://github.com/karelzak/util-linux/blob/master/sys-utils/switch_root.c

Oh wait, for systemd I was actually looking at:
https://github.com/systemd/systemd/blob/master/src/shared/switch-root.c

>
> Mind you, that's not the actual systemd repo. either I probably
> need to look a lot deeper (and at the actual systemd repo) to
> work out what's actually being called.
>
> > Sigh... Guess I'll have to dig that Fedora KVM image out and
> > try to see what it's about... ;-/ Here comes a couple of hours
> > of build...