KASAN poisoning for skb linear data

From: Dmitry Vyukov <dvyukov@google.com>
To: David Miller <davem@davemloft.net>,
	Willem de Bruijn <willemb@google.com>,
	Eric Dumazet <edumazet@google.com>,
	netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	andreyknvl <andreyknvl@google.com>
Subject: KASAN poisoning for skb linear data
Date: Mon, 15 Jan 2018 15:15:04 +0100	[thread overview]
Message-ID: <CACT4Y+Z6SS2AzYnMjbx_cmrataCLUhdjAx8XyYAnTMdVzndH5w@mail.gmail.com> (raw)

Hi,

As far as I understand pskb_may_pull() plays important role in packet
parsing for all protocols. And we did custom fragmentation of packets
emitted via tun (IFF_NAPI_FRAGS). However, it seems that it does not
give any results (bugs found), and I think the reason for this is that
linear data is rounded up and is usually quite large. So if a parsing
function does pskb_may_pull(1), or does not do it at all, it can
usually access more and it will go unnoticed. KASAN has an ability to
do custom poisoning: it can poison/unpoison any memory range, and then
detect any reads/writes to that range. What do you think about adding
custom KASAN poisoning to pskb_may_pull() and switching it to
non-eager mode (pull only what was requested) under KASAN? Do you
think it has potential for finding important bugs? What amount of work
is this?

Thanks