linux-kernel - Re: [PATCH] Version 8 (2.6.23) Smack: Simplified Mandatory Access Control Kernel

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Message-ID: <20071018045705.GM8181@ftp.linux.org.uk>
Date:	Thu, 18 Oct 2007 05:57:05 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	torvalds@...l.org, akpm@...l.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Version 8 (2.6.23) Smack: Simplified Mandatory Access Control Kernel

On Tue, Oct 16, 2007 at 09:17:40PM -0700, Casey Schaufler wrote:

At random:

> +static int smack_netlabel(struct sock *sk)
> +{
> +	static int initialized;
> +	struct socket_smack *ssp = sk->sk_security;
> +	struct netlbl_lsm_secattr secattr;
> +	int rc = 0;
> +
> +	if (!initialized) {
> +		smk_cipso_doi();
> +		initialized = 1;
> +	}

And just what happens if another task calls the same while we are
blocked on allocation in smk_cipso_doi()?

Another problem is your handling of smk_known - you add to head under
mutex; fine.  However, you read without one _and_ have no barriers
in initializing new list entries.

Think what happens if CPU1 adds to list and CPU2 sees write to smk_known
*before* it sees write to ->smk_next.  We see a single-element list and
we'll be lucky if that single entry won't be FUBAR.
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