[oss-security] CVE request: Another Linux syscall auditing bug

[Steve Grubb]

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