linux-kernel - Re: kernel BUG at kernel/cred.c:434!

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Date:   Wed, 17 Apr 2019 08:39:55 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Oleg Nesterov <oleg@...hat.com>, Paul Moore <paul@...l-moore.com>
Cc:     "chengjian (D)" <cj.chengjian@...wei.com>,
        Kees Cook <keescook@...omium.org>, NeilBrown <neilb@...e.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Xiexiuqi (Xie XiuQi)" <xiexiuqi@...wei.com>,
        Li Bin <huawei.libin@...wei.com>,
        Jason Yan <yanaijie@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>,
        SELinux <selinux@...r.kernel.org>,
        Yang Yingliang <yangyingliang@...wei.com>
Subject: Re: kernel BUG at kernel/cred.c:434!

On 4/17/2019 7:57 AM, Oleg Nesterov wrote:
> On 04/17, Paul Moore wrote:
>> I'm tempted to simply return an error in selinux_setprocattr() if
>> the task's credentials are not the same as its real_cred;
> What about other modules? I have no idea what smack_setprocattr() is,
> but it too does prepare_creds/commit creds.

For what it's worth, my test for Smack does not reproduce
the problem.

>
> it seems that the simplest workaround should simply add the additional
> cred == real_cred into proc_pid_attr_write().
>
> Oleg.
>