Re: [PATCH v3 00/25] user_namespace: introduce fsid mappings
From: Serge E. Hallyn
Date: Wed Feb 19 2020 - 16:48:41 EST
On Wed, Feb 19, 2020 at 01:35:58PM -0600, Serge E. Hallyn wrote:
> On Tue, Feb 18, 2020 at 03:33:46PM +0100, Christian Brauner wrote:
> > With fsid mappings we can solve this by writing an id mapping of 0
> > 100000 100000 and an fsid mapping of 0 300000 100000. On filesystem
> > access the kernel will now lookup the mapping for 300000 in the fsid
> > mapping tables of the user namespace. And since such a mapping exists,
> > the corresponding files will have correct ownership.
> So if I have
> /proc/self/uid_map: 0 100000 100000
> /proc/self/fsid_map: 1000 1000 1
Oh, sorry. Your explanation in 20/25 i think set me straight, though I need
to think through a few more examples.
> 3. If I create a new file, as nsuid 1000, what will be the inode owning kuid?
(Note - I edited the quoted txt above to be more precise)
I'm still not quite clear on this. I believe the fsid mapping will take
precedence so it'll be uid 1000 ? Per mount behavior would be nice there,
but perhaps unwieldy.