netdev - Re: [PATCH] vxlan: fix a out of bounds access in __vxlan_find

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Message-ID: <CAM_iQpUFHcX+=R9H5iO1HZLcnbaX=QEzDnRMUYqH+d3NeF7vQA@mail.gmail.com>
Date:	Fri, 29 Jan 2016 14:17:13 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	roy.qing.li@...il.com,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] vxlan: fix a out of bounds access in __vxlan_find_mac

On Fri, Jan 29, 2016 at 2:01 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Fri, 2016-01-29 at 13:41 -0800, Cong Wang wrote:
>> On Thu, Jan 28, 2016 at 5:43 PM,  <roy.qing.li@...il.com> wrote:
>> > From: Li RongQing <roy.qing.li@...il.com>
>> >
>> > The size of all_zeros_mac is 6 byte, but eth_hash() will access the
>> > 8 byte, and KASan reported the below bug:
>>
>>
>> Sounds like we should fix eth_hash() (macvlan has a same function),
>> it should not read beyond 6 bytes.
>
> Why ? We always have at least 2 bytes following ethernet address in a
> packet.

Because we have to fix all the cases that don't.

>
> Better add these 2 bytes in all_zeros_mac[] and not slow down the hash
> function.
>
> We use same tricks in eth_type_trans()
>

I never doubt it works, as long as you want to audit all the cases
like this one,
sure go for it.