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Open Source and information security mailing list archives
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Date: Thu, 9 Jun 2011 00:10:41 -0400 From: Andrew Lutomirski <luto@....edu> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Darren Hart <dvhart@...ux.intel.com>, George Spelvin <linux@...izon.com>, david@...advisors.com, kyle@...fetthome.net, linux-kernel@...r.kernel.org Subject: Re: Change in functionality of futex() system call. On Wed, Jun 8, 2011 at 11:54 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: > > You can not prevent DOS on a machine if you allow a process to RO map > your critical files (where you put futexes), because you allow this > process to interfere with critical cache lines bouncing between cpus. The cacheline bounce DoS slows things down and they go back to normal when you kill the DoS-ing task. The wakeup-eating DoS is permanent. Seems a good deal worse to me. If you make this change, please at least document it in the man page. > > Really, please forget about this crazy idea of allowing foreigners to > _read_ or memory _map_ your files. Dont do it. > Then how am I supposed to efficiently broadcast information to untrusted processes? I'll have to put any futexes involved into different files, but one way or another the actual data will have to be memory mapped to avoid syscall overhead. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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