linux-kernel - Re: [PATCH] net: caif: Don't act on notification for non-caif devices

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Date:	Tue, 24 Jan 2012 09:49:21 -0500
From:	Sasha Levin <levinsasha928@...il.com>
To:	Sjur Brændeland <sjurbren@...il.com>
Cc:	davem@...emloft.net, davej@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: caif: Don't act on notification for non-caif
 devices

On Tue, 2012-01-24 at 11:52 +0100, Sjur Brændeland wrote:
> 
> Nack, we have to handle other device types than just ARPHDR_CAIF after
> introducing
> CAIF over USB/NCM. I'd rather fix this in netns by removing the BUG_ON
> and return
> NULL. How about this instead: 
[snip]

I think that doing it this way is wrong for two reasons:

1. The code in net/ assumes net_generic is a trivial dereference and doesn't check that it's not NULL. This means that if anything goes wrong there you'll have a more dangerous NULL deref instead of a BUG().

2. You'll need to add other device to that if() statement anyway, as it currently looks like this:

	cfg = get_cfcnfg(dev_net(dev));
	caifdevs = caif_device_list(dev_net(dev));
	if (!cfg || !caifdevs)
		return 0;

	caifd = caif_get(dev);
	if (caifd == NULL && dev->type != ARPHRD_CAIF)
		return 0;

What my patch did was simply move the type check to above the net_generic call, it didn't add any new checks - which according to what you said, you'll need to do anyway.

-- 

Sasha.

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