netdev - Re: [PATCH ipsec] xfrm: prevent ipcomp scratch buffer race condition

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Message-ID: <20131017110420.GA21027@gondor.apana.org.au>
Date:	Thu, 17 Oct 2013 19:04:20 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Michal Kubecek <mkubecek@...e.cz>
Cc:	Steffen Klassert <steffen.klassert@...unet.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH ipsec] xfrm: prevent ipcomp scratch buffer race condition

On Thu, Oct 17, 2013 at 01:01:49PM +0200, Michal Kubecek wrote:
>
> When I was thinking about this, I came with two situations when this
> might IMHO happen:
> 
> 1. We are sending a packet to ourselves; this could mean not only a
> local loop but also e.g. a packets between an LXC container and the host
> or between two LXC containers. While it doesn't make much sense to use
> compression in such case, it might happen while testing a solution which
> is going to be used in a normal setup later.
> 
> 2. The packet was passed to tun/tap device by a userspace application.
> 
> Am I wrong?

I hope so :) Because otherwise xfrm_input will surely dead-lock since
it uses spin_lock.

The cases you mentioned should all go through netif_rx which will
then do the processing in BH context.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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