From: Florian Westphal <fw@strlen.de>
To: Phil Sutter <phil@nwl.cc>,
Pablo Neira Ayuso <pablo@netfilter.org>,
netfilter-devel@vger.kernel.org, fw@strlen.de
Subject: Re: [PATCH] netfilter: nf_tables: restrict expression reduction to first expression
Date: Wed, 18 May 2022 13:48:07 +0200 [thread overview]
Message-ID: <20220518114807.GE4316@breakpoint.cc> (raw)
In-Reply-To: <YoTbJTDxuQ131EDG@orbyte.nwl.cc>
Phil Sutter <phil@nwl.cc> wrote:
> > > | reduce = reduce && expr->ops->type->reduce;
> >
> > Could you elaborate?
>
> Well, an expression which may set verdict register to NFT_BREAK should
> prevent reduction of later expressions in same rule as it may stop rule
> evaluation at run-time. This is obvious for nft_cmp, but nft_meta is
> also a candidate: NFT_META_IFTYPE causes NFT_BREAK if pkt->skb->dev is
> NULL. The optimizer must not assume later expressions are evaluated.
This all seems fragile to me, with huge potential to add subtle bugs
that will be hard to track down.
next prev parent reply other threads:[~2022-05-18 11:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-18 10:08 [PATCH] netfilter: nf_tables: restrict expression reduction to first expression Pablo Neira Ayuso
2022-05-18 10:51 ` Phil Sutter
2022-05-18 11:01 ` Pablo Neira Ayuso
2022-05-18 11:40 ` Phil Sutter
2022-05-18 11:48 ` Florian Westphal [this message]
2022-05-18 12:26 ` Pablo Neira Ayuso
2022-05-18 12:38 ` Florian Westphal
2022-05-18 12:49 ` Pablo Neira Ayuso
2022-05-18 12:21 ` Pablo Neira Ayuso
2022-05-18 12:33 ` Pablo Neira Ayuso
2022-05-18 12:43 ` Phil Sutter
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