• Serge Hallyn's avatar
    User namespaces: set of cleanups (v2) · 18b6e041
    Serge Hallyn authored
    The user_ns is moved from nsproxy to user_struct, so that a struct
    cred by itself is sufficient to determine access (which it otherwise
    would not be).  Corresponding ecryptfs fixes (by David Howells) are
    here as well.
    Fix refcounting.  The following rules now apply:
            1. The task pins the user struct.
            2. The user struct pins its user namespace.
            3. The user namespace pins the struct user which created it.
    User namespaces are cloned during copy_creds().  Unsharing a new user_ns
    is no longer possible.  (We could re-add that, but it'll cause code
    duplication and doesn't seem useful if PAM doesn't need to clone user
    When a user namespace is created, its first user (uid 0) gets empty
    keyrings and a clean group_info.
    This incorporates a previous patch by David Howells.  Here
    is his original patch description:
    >I suggest adding the attached incremental patch.  It makes the following
    > (1) Provides a current_user_ns() macro to wrap accesses to current's user
    >     namespace.
    > (2) Fixes eCryptFS.
    > (3) Renames create_new_userns() to create_user_ns() to be more consistent
    >     with the other associated functions and because the 'new' in the name is
    >     superfluous.
    > (4) Moves the argument and permission checks made for CLONE_NEWUSER to the
    >     beginning of do_fork() so that they're done prior to making any attempts
    >     at allocation.
    > (5) Calls create_user_ns() after prepare_creds(), and gives it the new creds
    >     to fill in rather than have it return the new root user.  I don't imagine
    >     the new root user being used for anything other than filling in a cred
    >     struct.
    >     This also permits me to get rid of a get_uid() and a free_uid(), as the
    >     reference the creds were holding on the old user_struct can just be
    >     transferred to the new namespace's creator pointer.
    > (6) Makes create_user_ns() reset the UIDs and GIDs of the creds under
    >     preparation rather than doing it in copy_creds().
    >Signed-off-by: David Howells <dhowells@redhat.com>
    	Oct 20: integrate dhowells comments
    		1. leave thread_keyring alone
    		2. use current_user_ns() in set_user()
    Signed-off-by: default avatarSerge Hallyn <serue@us.ibm.com>
fork.c 40.8 KB