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From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nf-next 0/3] netfilter: nf_tables: reject loads from uninitialized registers
Date: Fri, 5 May 2023 16:32:28 +0200	[thread overview]
Message-ID: <ZFUTfE/u4q34TTDY@calendula> (raw)
In-Reply-To: <20230505111656.32238-1-fw@strlen.de>

Hi Florian,

On Fri, May 05, 2023 at 01:16:53PM +0200, Florian Westphal wrote:
> Keep a per-rule bitmask that tracks registers that have seen a store,
> then reject loads when the accessed registers haven't been flagged.
> 
> This changes uabi contract, because we previously allowed this.
> Neither nftables nor iptables-nft create such rules.
> 
> In case there is breakage, we could insert an 'store 0 to x'
> immediate expression into the ruleset automatically, but this
> isn't done here.
> 
> Let me know if you think the "refuse" approach is too risky.

Might the NFT_BREAK case defeat this approach? Sequence is:

1) expression that writes on register hits NFT_BREAK (nothing is written)
2) expression that read from register, it reads uninitialized data.

From ruleset load step, we cannot know if the write fails, because it
is subject to NFT_BREAK.

Thanks.

  parent reply	other threads:[~2023-05-05 14:32 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-05 11:16 [PATCH nf-next 0/3] netfilter: nf_tables: reject loads from uninitialized registers Florian Westphal
2023-05-05 11:16 ` [PATCH nf-next 1/3] netfilter: nf_tables: pass context structure to nft_parse_register_load Florian Westphal
2023-05-05 11:16 ` [PATCH nf-next 2/3] netfilter: nf_tables: validate register loads never access unitialised registers Florian Westphal
2023-05-30 23:49   ` Pablo Neira Ayuso
2023-05-31  9:51     ` Florian Westphal
2023-05-05 11:16 ` [PATCH nf-next 3/3] netfilter: nf_tables: don't initialize registers in nft_do_chain() Florian Westphal
2023-05-05 13:16 ` [PATCH nf-next 0/3] netfilter: nf_tables: reject loads from uninitialized registers Phil Sutter
2023-05-05 13:46   ` Florian Westphal
2023-05-05 14:14     ` Phil Sutter
2023-05-05 14:32 ` Pablo Neira Ayuso [this message]
2023-05-05 14:51   ` Florian Westphal
2023-05-05 15:34     ` Pablo Neira Ayuso
2023-05-07 11:22       ` Florian Westphal
2023-05-10  7:56         ` Pablo Neira Ayuso
2023-05-10  8:06           ` Florian Westphal
2023-05-10 15:46             ` Florian Westphal

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