Messages in this thread | | | Subject | Re: kernel BUG at kernel/cred.c:434! | From | Yang Yingliang <> | Date | Fri, 19 Apr 2019 10:34:44 +0800 |
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On 2019/4/19 10:04, Paul Moore wrote: > On Wed, Apr 17, 2019 at 10:50 PM Yang Yingliang > <yangyingliang@huawei.com> 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? It's possible the new cred is equal to current->real_cred and current->cred, so after overrides_creds(), they have the same value. > >> 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.
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