netdev - Re: [PATCH net-next v2 8/9] net: filter: rework/optimize internal BPF interpreter's instruction set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 25 Mar 2014 17:24:27 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	David Miller <davem@...emloft.net>, dborkman@...hat.com
CC:	ast@...mgrid.com, netdev@...r.kernel.org, hagen@...u.net,
	keescook@...omium.org, pmoore@...hat.com, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 8/9] net: filter: rework/optimize internal
 BPF interpreter's instruction set

On 03/25/2014 05:17 PM, David Miller wrote:
> From: Daniel Borkmann <dborkman@...hat.com>
> Date: Tue, 25 Mar 2014 13:10:56 +0100
> 
>>   - Conditional jt/jf targets replaced with jt/fall-through,
>>     and forward/backward jumps now possible as well
> 
> Ummm... does anyone even remember why backwards jumps were not allowed
> in the original BPF?
> 
> It's to guarentee forward progress in the filter.
> 
> Allowing branching backward would allow endless loops.
> 
> Please remove this feature.
> 

If you allow loops, it greatly increases the expressibility of the
language, but we would really need another control to limit CPU usage.

	-hpa

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html