Re: [PATCH] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

On 8/24/20 7:00 AM, Stephen Smalley wrote:

> > +int security_read_policy_kernel(struct selinux_state *state,
> > +                               void **data, size_t *len)
> > +{
> > +       int rc;
> > +
> > +       rc = security_read_policy_len(state, len);
> > +       if (rc)
> > +               return rc;
> > +
> > +       *data = vmalloc(*len);
> > +       if (!*data)
> > +               return -ENOMEM;
> >
> > +       return security_read_selinux_policy(state, data, len);
> >   }
>
> See the discussion here:
> https://lore.kernel.org/selinux/20200824113015.1375857-1-omosnace@xxxxxxxxxx/T/#t
>
> In order for this to be safe, you need to ensure that all callers of
> security_read_policy_kernel() have taken fsi->mutex in selinuxfs and
> any use of security_read_policy_len() occurs while holding the mutex.
> Otherwise, the length can change between security_read_policy_len()
> and security_read_selinux_policy() if policy is reloaded.

"struct selinux_fs_info" is available when calling 
security_read_policy_kernel() - currently in measure.c.
Only "struct selinux_state" is.

Is Ondrej's re-try approach I need to use to workaround policy reload issue?

thanks,
 -lakshmi