On Wed, Feb 22, 2012 at 1:53 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 02/22/2012 11:47 AM, Will Drewry wrote: >>> >>> I highly disagree with every filter having to check the mode: Filters that >>> don't check the arch on e.g. x86 are buggy, so they have to check it, even >>> if it's a 32-bit or 64-bit only system, the filters can't know that and >>> needs to check the arch at every syscall entry. All other info in the data >>> depends on the arch, because of this there isn't much code to share between >>> the two archs, so you can as well have one filter for each arch. >>> >>> Alternative approach: Tell the arch at filter install time and only run the >>> filters with the same arch as the current system call. If no filters are run, >>> deny the systemcall. >> >> This was roughly how I first implemented compat and non-compat >> support. It causes some implicit behavior across inheritance that is >> not nice though. >> > > This is trivially doable at the BPF level, right? Just make this the > first instruction in the program (either deny or jump to a separate > program branch)... and then there is still "one program" without any > weird inheritance issues? Exactly, and that's what the patch does now (after your feedback :) ld arch je arch, 1, 0 ret SECCOMP_RET_KILL <rest of bpf program> At this point, I don't think it makes sense to do it a different way than just in the BPF program even if it does mean leaving out the check could leave the program open to compat-style bugs. At least a shared library and/or good practices should be able to catch that error. thanks! will -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
