Re: [PATCH 4/9][cr][v2]: Restore file_owner info

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Matt Helsley (matthltc@us.ibm.com):
> For reference, here's sigio_perm():
> 
> static inline int sigio_perm(struct task_struct *p,
>                              struct fown_struct *fown, int sig)
> { 
>         const struct cred *cred;
>         int ret;
> 
>         rcu_read_lock();
>         cred = __task_cred(p);
>         ret = ((fown->euid == 0 ||
>                 fown->euid == cred->suid || fown->euid == cred->uid ||
>                 fown->uid  == cred->suid || fown->uid  == cred->uid) &&
>                !security_file_send_sigiotask(p, fown, sig));
>         rcu_read_unlock();
>         return ret;
> }
> 
> [ My Notes: unlike check_kill_permission() it does not check CAP_KILL.

Right, that's bc we don't store capabilities in the fown_struct.
So fown->euid==0 is all we can do.  Since this can be called from
interrupt, current is not useful.

> Also check_kill_permission() calls audit as if the signal is about to be
> delivered but sigio_perm() does not. ]

-serge