On Wed, Apr 17, 2019 at 10:50 PM Yang Yingliang <yangyingliang@xxxxxxxxxx> wrote: > On 2019/4/18 8:24, Casey Schaufler wrote: > > On 4/17/2019 4:39 PM, Paul Moore wrote: > >> > >> Since it looks like all three LSMs which implement the setprocattr > >> hook are vulnerable I'm open to the idea that proc_pid_attr_write() is > >> a better choice for the cred != read_cred check, but I would want to > >> make sure John and Casey are okay with that. > >> > >> John? > >> > >> Casey? > > > > I'm fine with the change going into proc_pid_attr_write(). > > The cred != real_cred checking is not enough. > > Consider this situation, when doing override, cred, real_cred and > new_cred are all same: > > after override_creds() cred == real_cred == new1_cred I'm sorry, you've lost me. After override_creds() returns current->cred and current->real_cred are not going to be the same, yes? > after prepare_creds() new2_cred > after commit_creds() becasue the check is false, so cred == > real_cred == new2_cred > after revert_creds() cred == new1_cred, real_cred == new2_cred > > It will cause cred != real_cred finally. -- paul moore www.paul-moore.com
