Re: [PATCH v3 00/25] user_namespace: introduce fsid mappings

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

1. If I read files from the rootfs which have host uid 101000, they
will appear as uid 100 to me?

2. If I read host files with uid 1000, they will appear as uid 1000 to me?

3. If I create a new file, as uid 1000, what will be the inode owning uid?