Messages in this thread | | | Subject | Re: [PATCH 2/3] [RFC] seccomp: give BPF x32 bit when restoring x32 filter | From | Eric Paris <> | Date | Fri, 11 Jul 2014 12:16:47 -0400 |
| |
On Fri, 2014-07-11 at 12:11 -0400, Paul Moore wrote: > 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).
Maybe libseccomp does some HORRIFIC contortions under the hood, but the interface is crap... Since seccomp_data->arch can't distinguish between X32 and X86_64. If I write a seccomp filter which says
KILL arch != x86_64 KILL init_module ALLOW everything else
I can still call init_module, I just have to use the X32 variant.
If libseccomp is translating:
KILL arch != x86_64 into:
KILL arch != x86_64 KILL syscall_nr >= 2000
That's just showing how dumb the kernel interface is... Good for you guys, but the kernel is just being dumb :)
| |