netdev - Re: [PATCH net] bpf: fix method of PTR_TO

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Date:	Wed, 03 Aug 2016 11:54:25 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jakub.kicinski@...ronome.com
Cc:	ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: fix method of PTR_TO_PACKET reg id generation

From: Jakub Kicinski <jakub.kicinski@...ronome.com>
Date: Tue,  2 Aug 2016 16:12:14 +0100

> Using per-register incrementing ID can lead to
> find_good_pkt_pointers() confusing registers which
> have completely different values.  Consider example:
 ...
> We need to get a UNKNOWN_VALUE with imm to force id
> generation so lines 0-5 make r7 a valid packet pointer.
> We then read two different bytes from the packet and
> add them to copies of the constructed packet pointer.
> r8 (line 9) and r9 (line 11) will get the same id of 1,
> independently.  When either of them is validated (line
> 13) - find_good_pkt_pointers() will also mark the other
> as safe.  This leads to access on line 14 being mistakenly
> considered safe.
> 
> Fixes: 969bf05eb3ce ("bpf: direct packet access")
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

Applied and queued up for -stable, thanks.