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From: Yang Yingliang <yangyingliang@huawei.com>
To: Paul Moore <paul@paul-moore.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>,
	Oleg Nesterov <oleg@redhat.com>, <john.johansen@canonical.com>,
	"chengjian (D)" <cj.chengjian@huawei.com>,
	Kees Cook <keescook@chromium.org>, NeilBrown <neilb@suse.com>,
	Anna Schumaker <Anna.Schumaker@netapp.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	"Xiexiuqi (Xie XiuQi)" <xiexiuqi@huawei.com>,
	Li Bin <huawei.libin@huawei.com>,
	"Jason Yan" <yanaijie@huawei.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Linux Security Module list 
	<linux-security-module@vger.kernel.org>,
	SELinux <selinux@vger.kernel.org>
Subject: Re: kernel BUG at kernel/cred.c:434!
Date: Fri, 19 Apr 2019 10:34:44 +0800	[thread overview]
Message-ID: <5CB933C4.7000300@huawei.com> (raw)
In-Reply-To: <CAHC9VhQkrR+m9_dYLg4VG-26TdUnf8XFjbmuVQ70YCOp6DhN_g@mail.gmail.com>



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.



  reply	other threads:[~2019-04-19  2:42 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-12  6:21 kernel BUG at kernel/cred.c:434! chengjian (D)
2019-04-12 15:28 ` Casey Schaufler
2019-04-15 13:43   ` Oleg Nesterov
2019-04-15 14:48     ` Paul Moore
2019-04-15 15:05       ` Oleg Nesterov
2019-04-15 16:20         ` Paul Moore
2019-04-16  3:40           ` Kees Cook
2019-04-16 14:46             ` chengjian (D)
2019-04-17 14:30               ` Paul Moore
2019-04-17 14:57                 ` Oleg Nesterov
2019-04-17 15:39                   ` Casey Schaufler
2019-04-17 15:40                   ` Paul Moore
2019-04-17 16:27                     ` Oleg Nesterov
2019-04-17 16:42                       ` Casey Schaufler
2019-04-18 13:39                         ` Stephen Smalley
2019-04-17 23:39                       ` Paul Moore
2019-04-18  0:17                         ` John Johansen
2019-04-18  0:24                         ` Casey Schaufler
2019-04-18  2:49                           ` Yang Yingliang
2019-04-19  2:04                             ` Paul Moore
2019-04-19  2:34                               ` Yang Yingliang [this message]
2019-04-19 13:24                                 ` Paul Moore
2019-04-19 14:34                                   ` Yang Yingliang
2019-04-19 16:13                                     ` Paul Moore
2019-04-20  7:38                                       ` Yang Yingliang
2019-04-22 19:48                                         ` Paul Moore
2019-04-23  4:08                                           ` Yang Yingliang
2019-04-23 20:18                                             ` Paul Moore

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