netdev - Re: [PATCH] icmp: Fixed bug in raw sockets causing incorrect ICMP SNMP counter values

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Date:	Sun, 11 Oct 2015 15:43:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Cox <ben@...jojo.co.uk>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, ben+patches@...jojo.co.uk,
	David L Stevens <dlstevens@...ibm.com>
Subject: Re: [PATCH] icmp: Fixed bug in raw sockets causing incorrect ICMP
 SNMP counter values

On Sun, 2015-10-11 at 23:17 +0100, Ben Cox wrote:
> Forgive me for possibly being a little stupid here (This is my first
> patch to Linux so I am slightly over my head)
> 
> Is this issue not addressed above the file where the following check is done?
> 
> if (iphlen > length)
>     goto error_free;
> 

Imagine someone sends a frame, pretending it is ICMP, but containing
only the IPv4 header. And not a _single_ byte more.

length = 20

iphlen = 20 (if say ihl == 5)

We copied 20 bytes from user land.

But your code reads 21th byte.



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