linux-kernel - Re: [PATCH BUGFIX -v2 -rc4] Smack: Respect 'unlabeled' netlabel mode

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Message-Id: <20080530162500.1411f14d.akpm@linux-foundation.org>
Date:	Fri, 30 May 2008 16:25:00 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Ahmed S. Darwish" <darwish.07@...il.com>
Cc:	casey@...aufler-ca.com, paul.moore@...com,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH BUGFIX -v2 -rc4] Smack: Respect 'unlabeled' netlabel
 mode

On Sat, 31 May 2008 02:57:51 +0300
"Ahmed S. Darwish" <darwish.07@...il.com> wrote:

> +		mutex_lock(&smack_ambient_lock);
> +		nlsp->domain = kstrdup(smack_net_ambient, GFP_ATOMIC);
> +		mutex_unlock(&smack_ambient_lock);

no no no no no.  And no.

GFP_ATOMIC is *unreliable*.  Using it in a "security" feature is a bug
- if it fails, the feature isn't secure any more.

Failing to check the kmalloc() return value might be a bug.

If we _need_ GFP_ATOMIC here then taking a mutex in a cannot-sleep
context is a bug.

The patch adds a kmalloc but doesn't add a kfree.  Is it leaky?

Finally, why is there a need to take a lock around a single store
instruction?
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