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  1. 10 Dec, 2018 3 commits
  3. 14 Oct, 2018 1 commit
    • autodev: adapt to changes in Linux 4.18 · db421960
      Christian Brauner authored 
      Starting with commit
55956b59df33 ("vfs: Allow userns root to call mknod on owned filesystems.")
Linux will allow mknod() in user namespaces for userns root if CAP_MKNOD is
available.
However, these device nodes are useless since

static struct super_block *alloc_super(struct file_system_type *type, int flags,
                                       struct user_namespace *user_ns)
{
    /* <snip> */

    if (s->s_user_ns != &init_user_ns)
            s->s_iflags |= SB_I_NODEV;

    /* <snip> */
}

will set the SB_I_NODEV flag on the filesystem. When a device node created in
non-init userns is open()ed the call chain will hit:

bool may_open_dev(const struct path *path)
{
    return !(path->mnt->mnt_flags & MNT_NODEV) &&
            !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
}

which will cause an EPERM because the device node is located on an fs
owned by non-init-userns and thus doesn't grant access to device nodes due to
SB_I_NODEV.

This commit enables LXC to deal with such kernels.
Signed-off-by: 's avatarChristian Brauner <christian.brauner@ubuntu.com>
  5. 23 Aug, 2018 36 commits