Re: r-o bind in nfsd

[Tetsuo Handa]

Hello.

> Maybe some enhancement to the 'intent' structure with a similar
> effect could be done instead.
> 
> Then you could, presumably, put a security hook somewhere in
> link_path_walk for those modules (like AppArmor) which want to do
> checks based on the namespace.

I think link_path_walk() is not a good place to insert new LSM hooks
for pathname based access control (AppArmor and TOMOYO) purpose because

  (1) The kernel don't know what operation (open/create/truncate etc.) will be
      done at the moment of link_path_walk().

  (2) Not all operations call link_path_walk() before these operations
      are done. For example, ftruncate() doesn't call link_path_walk().

  (3) The rename() and link() operations handle two pathnames.
      But, it is not possible to know both pathnames at the moment of
      link_path_walk().

I think we need to introduce new LSM hooks outside link_path_walk().
http://kerneltrap.org/mailarchive/linux-fsdevel/2008/2/17/882024
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