If I can't resolve the range, maybe it'd be better to just not return
the info at all? Are the first and third fields of any value without
the second?
> Note that statmount() requires that the whole range must be resolvable
> in the caller's user namespace. If a subrange fails to map it will still
> list the map as not resolvable. This is a practical compromise to avoid
> having to find which subranges are resovable and wich aren't.
>
> Idmappings are listed as a string array with each mapping separated by
> zero bytes. This allows to retrieve the idmappings and immediately use
> them for writing to e.g., /proc/<pid>/{g,u}id_map and it also allow for
> simple iteration like:
>
> if (stmnt->mask & STATMOUNT_MNT_UIDMAP) {
> const char *idmap = stmnt->str + stmnt->mnt_uidmap;
>
> for (size_t idx = 0; idx < stmnt->mnt_uidmap_nr; idx++) {
> printf("mnt_uidmap[%lu]: %s\n", idx, idmap);
> idmap += strlen(idmap) + 1;
> }
> }
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> ---
> Christian Brauner (4):
> uidgid: add map_id_range_up()
> statmount: allow to retrieve idmappings
> samples/vfs: check whether flag was raised
> samples/vfs: add STATMOUNT_MNT_{G,U}IDMAP
>
> fs/internal.h | 1 +
> fs/mnt_idmapping.c | 49 ++++++++++++++++++++++++++++++++++++++
> fs/namespace.c | 43 ++++++++++++++++++++++++++++++++-
> include/linux/uidgid.h | 6 +++++
> include/uapi/linux/mount.h | 8 ++++++-
> kernel/user_namespace.c | 26 +++++++++++++-------
> samples/vfs/samples-vfs.h | 14 ++++++++++-
> samples/vfs/test-list-all-mounts.c | 35 ++++++++++++++++++++++-----
> 8 files changed, 164 insertions(+), 18 deletions(-)
> ---
> base-commit: 6d61a53dd6f55405ebcaea6ee38d1ab5a8856c2c
> change-id: 20250129-work-mnt_idmap-statmount-e57f258fef8e
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
