• Latchesar Ionkov's avatar
    9p: attach-per-user · ba17674f
    Latchesar Ionkov authored
    The 9P2000 protocol requires the authentication and permission checks to be
    done in the file server. For that reason every user that accesses the file
    server tree has to authenticate and attach to the server separately.
    Multiple users can share the same connection to the server.
    Currently v9fs does a single attach and executes all I/O operations as a
    single user. This makes using v9fs in multiuser environment unsafe as it
    depends on the client doing the permission checking.
    This patch improves the 9P2000 support by allowing every user to attach
    separately. The patch defines three modes of access (new mount option
    - attach-per-user (access=user) (default mode for 9P2000.u)
     If a user tries to access a file served by v9fs for the first time, v9fs
     sends an attach command to the server (Tattach) specifying the user. If
     the attach succeeds, the user can access the v9fs tree.
     As there is no uname->uid (string->integer) mapping yet, this mode works
     only with the 9P2000.u dialect.
    - allow only one user to access the tree (access=<uid>)
     Only the user with uid can access the v9fs tree. Other users that attempt
     to access it will get EPERM error.
    - do all operations as a single user (access=any) (default for 9P2000)
     V9fs does a single attach and all operations are done as a single user.
     If this mode is selected, the v9fs behavior is identical with the current
    Signed-off-by: default avatarLatchesar Ionkov <lucho@ionkov.net>
    Signed-off-by: default avatarEric Van Hensbergen <ericvh@gmail.com>