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Message-ID: <5505250.3yQZm9nuEg@x2>
Date: Thu, 19 Jun 2014 23:37:39 -0400
From: Steve Grubb <sgrubb@...hat.com>
To: oss-security@...ts.openwall.com
Cc: Andy Lutomirski <luto@...capital.net>,
Linux Audit <linux-audit@...hat.com>
Subject: Re: CVE request: Another Linux syscall auditing bug
Hi,
Reminder again...please report bugs to linux-audit mail list.
On Thursday, June 19, 2014 06:26:38 PM Andy Lutomirski wrote:
> On a 32-bit x86 kernel with syscall auditing enabled, syscall(1000)
> will cause an OOPS. This problem goes at least as far back as Linux
> 3.11 and appears to be present in Linux 3.15 as well. I suspect that
> this bug is very old.
>
> In order to see this bug, you'll need syscall auditing on (auditctl -e
> 1 will do that) and you'll need 'sep' in flags in /proc/cpuinfo. That
> means that qemu -cpu qemu64 will not be exposed to this bug, but qemu
> -cpu host will on any recent CPU.
>
> Mitigations include:
> - Running under ptrace or strace.
> - Using any seccomp filter at all (phew!)
> - Turning off SEP (which is a big slowdown on all syscalls)
> - auditctl -a task,never
>
> I'd be rather surprised if this can be used for anything other than
> DoS, although the same underlying bug could potentially have more
> serious consequences.
>
> This bug was found (inadvertently, I presume) by Toralf Förster. The
> patch here:
>
> http://lkml.kernel.org/g/CALCETrW7U4AHG-a9oPbOt31z3wgzhjSu8b+yGpdM4+vNinKgsA
> @mail.gmail.com
>
> is reported to fix the bug, but it should not be considered to be
> well-tested.
>
> --Andy
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