Subject: Re: [PATCH v3 2/3] packet: fill the gap of TPACKET_ALIGNMENT with zeros

From: Daniel Borkmann <[email-masked]>
Date: Mon, 16 Dec 2013 11:22:35 +0100

On 12/16/2013 11:16 AM, David Laight wrote:
>>> +		memset(h.h2->tp_padding, 0,
>>> +		       hdrlen - offsetof(struct tpacket2_hdr, tp_padding));
>
> What is wrong with 'sizeof h.h2->tp_padding' ?
> The compiler will probably inline the memset into a couple of word
> sized writes of zero - probably not measurable.
> Not zeroing them might be leaking kernel memory contents (depends
> where the memory came from - might just be stale packet data).

The ring buffer memory we're operating on comes from mmap(2) btw.

> 	David