On Fri, Jul 11, 2014 at 3:55 PM, H. Peter Anvin <h...@zytor.com> wrote: > It includes the X32 bit.
If the uapi for __NR_* includes the x32 bit, then that's what seccomp filters must be seeing. Building seccomp filters is documented to use the __NR_* values. -Kees > > On July 11, 2014 3:52:42 PM PDT, Kees Cook <keesc...@chromium.org> wrote: >>On Fri, Jul 11, 2014 at 3:48 PM, Kees Cook <keesc...@chromium.org> >>wrote: >>> On Fri, Jul 11, 2014 at 12:36 PM, Paul Moore <pmo...@redhat.com> >>wrote: >>>> Anyway, getting back to the idea I mentioned earlier ... as many of >>you may >>>> know, Kees (added to the CC line) is working on some seccomp filter >>>> improvements which will result in a new seccomp syscall. Perhaps >>one way >>>> forward is to preserve everything as it is currently with the >>prctl() >>>> interface, but with the new seccomp() based interface we fixup x32 >>and use the >>>> new AUDIT_ARCH_X32 token? It might result in a bit of ugliness in >>some of the >>>> kernel, but I don't think it would be too bad, and I think it would >>address >>>> both our concerns. >>> >>> Adding AUDIT_ARCH_X32: yes please. (On that note, the comment "/* >>Both >>> x32 and x86_64 are considered "64-bit". */" should be changed...) >>> >>> Just so I understand: currently x86_64 and x32 both present as >>> AUDIT_ARCH_X86_64. The x32 syscalls are seen as in a different range >>> (due to the set high bit). >>> >>> The seccomp used in Chrome, Chrome OS, and vsftpd should all only do >>> whitelisting by both arch and syscall, so adding AUDIT_ARCH_X32 >>> without setting __X32_SYSCALL_BIT would be totally fine (it would >>> catch the arch instead of the syscall). This sounds similar to how >>> libseccomp is doing things, so these should be fine. >> >>I should clarify: seccomp expects to find whatever is sent as the >>syscall nr... as in the __NR_read used like this: >> >> BPF_STMT(BPF_LD+BPF_W+BPF_ABS, >> offsetof(struct seccomp_data, nr)), >> BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 0, 1), >> BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL), >> BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), >> >>Are there native x32 users yet? What does __NR_read resolve to via the >>uapi on a native x32 userspace? >> >>-Kees >> >>> The only project I know of doing blacklisting is lxc, and Eric's >>> example looks a lot like a discussion I saw with lxc and init_module. >>> :) So it sounds like we can get this right there. >>> >>> I'd like to avoid carrying a delta on filter logic based on the prctl >>> vs syscall entry. Can we find any userspace filters being used that a >>> "correct" fix would break? (If so, then yes, we'll need to do this >>> proposed "via prctl or via syscall?" change.) >>> >>> -Kees >>> >>> -- >>> Kees Cook >>> Chrome OS Security > > -- > Sent from my mobile phone. Please pardon brevity and lack of formatting. -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/