Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1224287

Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well

Show all headers | View raw

Hi Daniel,

On Fri, Sep 11, 2015 at 08:28:19PM +0200, Daniel Borkmann wrote:
> I think due to the given insns restrictions on classic seccomp, this
> could work for "most cases" (see below) for the time being until pointer
> sanitation is resolved and that seccomp-only restriction from the dump
> could be removed,

Ok, thanks.

> BUT there's one more stone in the road which you still
> need to take care of with this whole 'giving classic seccomp-BPF -> eBPF
> transforms an fd, dumping and restoring that via bpf(2)' approach:
> 
> If you have JIT enabled on ARM32, and add a classic seccomp-BPF filter,
> and dump that via your bpf(2) interface based on the current patches, what
> you'll get is not eBPF opcodes but classic (!) BPF opcodes as ARM32 classic
> JIT supports compilation of seccomp, since commit 24e737c1ebac ("ARM: net:
> add JIT support for loads from struct seccomp_data.").
> 
> So in that case, bpf_prepare_filter() will not call into bpf_migrate_filter()
> as there's simply no need for it, because the classic code could already
> be JITed there. I guess other archs where JIT support for eBPF in not yet
> within near sight might sooner or later support this insn for their classic
> JITs, too ...

Thanks for pointing this out.

What if we legislate that the output of bpf(BPF_PROG_DUMP, ...) is
always eBPF? As near as I can tell there is no way to determine if a
struct bpf_prog is classic or eBPF, so we'd need to add a bit to
indicate whether or not the prog has been converted so that
BPF_PROG_DUMP knows when to convert it.

Tycho
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-11 02:30 +0200
  Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Daniel Borkmann <daniel@iogearbox.net> - 2015-09-11 15:10 +0200
    Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-11 16:50 +0200
      Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Daniel Borkmann <daniel@iogearbox.net> - 2015-09-11 18:10 +0200
        Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-11 19:40 +0200
          Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Daniel Borkmann <daniel@iogearbox.net> - 2015-09-11 20:30 +0200
            Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-14 18:10 +0200
              Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Daniel Borkmann <daniel@iogearbox.net> - 2015-09-14 18:50 +0200
                Re: [PATCH v2 2/5] seccomp: make underlying bpf ref counted as well Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-14 19:40 +0200

csiph-web