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Subject: Re: mount.nfs: Protocol error after upgrade to linux/master
To:     Kees Cook <keescook@chromium.org>
Cc:     Casey Schaufler <casey@schaufler-ca.com>,
        Jakub Kicinski <jakub.kicinski@netronome.com>,
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        Trond Myklebust <trond.myklebust@hammerspace.com>,
        "open list:NFS, SUNRPC, AND..." <linux-nfs@vger.kernel.org>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        LKML <linux-kernel@vger.kernel.org>
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From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
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Date:   Sat, 23 Mar 2019 11:44:12 +0900
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On 2019/03/23 7:45, Kees Cook wrote:
> It breaks the backward-compat for the "security=" line. If a system is
> booted with CONFIG_LSM="minors...,apparmor" and "security=selinux",
> neither apparmor nor selinux will be initialized. The logic on
> "security=..." depends on the other LSMs being present in the list.

Really? The logic on "security=..." does not depend on LSM_FLAG_LEGACY_MAJOR
LSMs being present in the CONFIG_LSM= list, for ordered_lsm_parse() does

  (Step 1) Enable LSM_ORDER_FIRST module (i.e. capability).

  (Step 2) Disable LSM_FLAG_LEGACY_MAJOR modules which was not specified
           by "security=" parameter when "security=" parameter was specified.

  (Step 3) Enable modules specified by "lsm=" parameter (or CONFIG_LSM= settings
           if "lsm=" parameter was not specified).

  (Step 4) Enable up to one LSM_FLAG_LEGACY_MAJOR module which was specified
           by "security=" parameter when "security=" parameter was specified.

  (Step 5) Disable all unused modules.

and (Step 4) will compensate for lack of that module in (Step 3).