kernel crash in mknod

[Christian Brauner]

> we can change the parameter of security_path_post_mknod() from
> dentry to inode?

If all current callers only operate on the inode then it seems the best
to only pass the inode. If there's some reason someone later needs a
dentry the hook can always be changed.

For bigger changes it's also worthwhile if the object that's passed down
into the hook-based LSM layer is as specific as possible. If someone
does a change that affects lifetime rules of mounts then any hook that
takes a struct path argument that's unused means going through each LSM
that implements the hook only to find out it's not actually used.
Similar for dentry vs inode imho.