libcephfs and supplimentary groups

David Disseldorp ddiss at
Thu Jul 25 15:07:49 UTC 2019


Without calling ceph_mount_perms_set(), libcephfs consumers such as
Samba can rely upon UserPerm::uid() and UserPerm::gid() to fallback to
geteuid() and setegid() respectively for things such as ACL enforcement.
However, there is no such fallback for supplementary groups, so ACL
checks for a user which is only permitted path access via a
supplementary group will result in a permission denied error.

Samba ticket:

I've written a patch to address this (it currently omits the get_gids()

Does this approach make sense, or should Samba go down the
ceph_mount_perms_set() route to avoid this bug? The latter
would likely be problematic, as user/group details for a mount will
remain static.

Cheers, David

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