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Date: Tue, 28 Jan 2025 01:37:06 +0100
From: Florian Westphal <fw@strlen.de>
To: Sunny73Cr <Sunny73Cr@protonmail.com>
Cc: Florian Westphal <fw@strlen.de>,
	"netfilter@vger.kernel.org" <netfilter@vger.kernel.org>
Subject: Re: Raw Payload Expressions - out of bounds write?
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Sunny73Cr <Sunny73Cr@protonmail.com> wrote:
> > Please elaborate as what is wrong here in listing 3.
> 
> Within the second line of the rule (@ih,80,16 set @ih,80,16 & 0x3f0 \)
> 
> The mask 0x3f0 equates to 1,008 in decimal.
> (3 * 16**2) + (15 * 16**1) + (0 * 16^0) = 1,008
> Here '**' indicates exponent.
> 
> 1,008 is far larger than the 34 bit range that I covered.

Sigh.  Why did you not say something like:

The mask is provided as '0x3f0' in the listing, but I had expected
0xfc0f, as only 6 bits should be cleared, but the mask KEEPS 6 bits.

It would have saved me a headache figuring out bug you refer to.
I am not a mind reader :-/

Use --debug=netlink, it looks like its a display bug.

I'll have a look.