Re: [PATCH v3 06/15] commoncap: Refactor to remove bprm_secureexec hook

[James Morris]

On Tue, 18 Jul 2017, Kees Cook wrote:

> The commoncap implementation of the bprm_secureexec hook is the only LSM
> that depends on the final call to its bprm_set_creds hook (since it may
> be called for multiple files, it ignores bprm->called_set_creds). As a
> result, it cannot safely _clear_ bprm->secureexec since other LSMs may
> have set it.  Instead, remove the bprm_secureexec hook by introducing a
> new flag to bprm specific to commoncap: cap_elevated. This is similar to
> cap_effective, but that is used for a specific subset of elevated
> privileges, and exists solely to track state from bprm_set_creds to
> bprm_secureexec. As such, it will be removed in the next patch.
> 
> Here, set the new bprm->cap_elevated flag when setuid/setgid has happened
> from bprm_fill_uid() or fscapabilities have been prepared. This temporarily
> moves the bprm_secureexec hook to a static inline. The helper will be
> removed in the next patch; this makes the step easier to review and bisect,
> since this does not introduce any changes to inputs nor outputs to the
> "elevated privileges" calculation.
> 
> The new flag is merged with the bprm->secureexec flag in setup_new_exec()
> since this marks the end of any further prepare_binprm() calls.
> 
> Cc: Serge Hallyn <serge@xxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>


Acked-by: James Morris <james.l.morris@xxxxxxxxxx>


-- 
James Morris
<jmorris@xxxxxxxxx>