linux-kernel - Re: [PATCH] fix security_release

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Date:   Wed, 4 Oct 2017 17:17:39 +1100 (AEDT)
From:   James Morris <jmorris@...ei.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Serge Hallyn <serge@...lyn.com>,
        James Morris <james.l.morris@...cle.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH] fix security_release_secctx seems broken

On Tue, 19 Sep 2017, Casey Schaufler wrote:

> Subject: [PATCH] fix security_release_secctx seems broken
> 
> security_inode_getsecurity() provides the text string value
> of a security attribute. It does not provide a "secctx".
> The code in xattr_getsecurity() that calls security_inode_getsecurity()
> and then calls security_release_secctx() happened to work because
> SElinux and Smack treat the attribute and the secctx the same way.
> It fails for cap_inode_getsecurity(), because that module has no
> secctx that ever needs releasing. It turns out that Smack is the
> one that's doing things wrong by not allocating memory when instructed
> to do so by the "alloc" parameter.
> 
> The fix is simple enough. Change the security_release_secctx() to
> kfree() because it isn't a secctx being returned by
> security_inode_getsecurity(). Change Smack to allocate the string when
> told to do so.
> 
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>

Looks good to me.  I wonder why security_release_secctx was used in the 
first place? (it arrived via commit 42492594)

Konstantin: how did you trigger this?

I plan to send this to Linus for -rc4 unless anyone has objections.


-- 
James Morris
<jmorris@...ei.org>