Re: [PATCH 2/3] [RFC] seccomp: give BPF x32 bit when restoring x32 filter

From: Paul Moore
Date: Fri Jul 11 2014 - 12:11:46 EST

On Thursday, July 10, 2014 09:06:02 PM H. Peter Anvin wrote:
> Incidentally: do seccomp users know that on an x86-64 system you can
> recevie system calls from any of the x86 architectures, regardless of
> how the program is invoked? (This is unusual, so normally denying those
> "alien" calls is the right thing to do.)

I obviously can't speak for all seccomp users, but libseccomp handles this by
checking the seccomp_data->arch value at the start of the filter and killing
(by default) any non-native architectures. If you want, you can change this
default behavior or add support for other architectures (e.g. create a filter
that allows both x86-64 and x32 but disallows x86, or any combination of the
three for that matter).

paul moore
security and virtualization @ redhat

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