linux-kernel - Re: [PATCH v2] LSM: general protection fault in legacy_parse

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Message-ID: <20220128085914.rxrz7qt3uk7fp67d@wittgenstein>
Date:   Fri, 28 Jan 2022 09:59:14 +0100
From:   Christian Brauner <brauner@...nel.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Christian Brauner <christian@...uner.io>,
        James Morris <jmorris@...ei.org>,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzbot <syzbot+d1e3b1d92d25abf97943@...kaller.appspotmail.com>,
        David Howells <dhowells@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        selinux@...r.kernel.org
Subject: Re: [PATCH v2] LSM: general protection fault in legacy_parse_param

On Thu, Jan 27, 2022 at 08:51:44AM -0800, Casey Schaufler wrote:
> The usual LSM hook "bail on fail" scheme doesn't work for cases where
> a security module may return an error code indicating that it does not
> recognize an input.  In this particular case Smack sees a mount option
> that it recognizes, and returns 0. A call to a BPF hook follows, which
> returns -ENOPARAM, which confuses the caller because Smack has processed
> its data.
> 
> The SELinux hook incorrectly returns 1 on success. There was a time
> when this was correct, however the current expectation is that it
> return 0 on success. This is repaired.
> 
> Reported-by: syzbot+d1e3b1d92d25abf97943@...kaller.appspotmail.com
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> ---

Looks good,
Acked-by: Christian Brauner <brauner@...nel.org>