On Fri, May 26, 2017 at 10:48:17AM -0400, Stephen Smalley wrote: > On Thu, 2017-05-25 at 17:07 -0400, Scott Mayhew wrote: > > Red Hat QE reported that chcon fails over NFSv4.2 on recent kernels. > > The problem is related to how filesystems are mounted in NFSv4. > > What kernel version and what is a reproducer for the problem? I don't > seem to see it on e.g. Fedora 25 with 4.10, unless I misunderstand. Basically just mount an export with security_label set, mount over NFS, "ls -Z" will (correctly) show you the server-side security labels, but "chcon" will fail with ENOTSUP. If that's not reproducing, maybe you chould show us "exports -v" and "mount" output--it might not reproduce if you have an "fsid=0" export or if you're mounting with a protocol version older than 4.2. --b. > > > > > When an NFSv4 client performs a mount operation, it first mounts the > > NFSv4 root and then does path walk to the exported path and performs > > a > > submount on that, cloning the security mount options from the root's > > superblock to the submount's superblock in the process. > > > > Unless the NFS server has an explicit fsid=0 export with the > > "security_label" option, the NFSv4 root superblock will not have > > SBLABEL_MNT set, and neither will the submount superblock after > > cloning > > the security mount options. As a result, setxattr's of security > > labels > > over NFSv4.2 will fail. > > > > NFS servers with a modern nfs-utils package will automatically create > > a > > pseudo fs to fill in the gaps (including the root itself) leading up > > to > > the actual export, so it is uncommon these days for an NFS server to > > have an explicit fsid=0 export. > > > > Allowing the NFSv4 client to override the SECURITY_LSM_NATIVE_LABELS > > flag on an initialized superblock would ensure that SBLABEL_MNT is > > set > > when the client traverses from an exported path without the > > "security_label" option to one with the "security_label" option. > > > > Scott Mayhew (2): > > selinux: allow SECURITY_LSM_NATIVE_LABELS to be set on an already > > initialized superblock > > nfs: update labeling behavior on a superblock when submounting > > > > fs/nfs/super.c | 23 ++++++++++++++++++++++- > > security/selinux/hooks.c | 4 ++-- > > 2 files changed, 24 insertions(+), 3 deletions(-) > >
