On Fri, Oct 02, 2015 at 02:10:24PM -0700, Kees Cook wrote: > On Fri, Oct 2, 2015 at 9:27 AM, Tycho Andersen > <tycho.andersen@xxxxxxxxxxxxx> wrote: > > Hi all, > > > > Here's v5 of the seccomp filter c/r set. The individual patch notes have > > changes, but two highlights are: > > > > * This series is now based on http://patchwork.ozlabs.org/patch/525492/ and > > will need to be built with that patch applied. This gets rid of two incorrect > > patches in the previous series and is a nicer API. > > > > * I couldn't figure out a nice way to have SECCOMP_GET_FILTER_FD return the > > same struct file across calls, so we still need a kcmp command. I've narrowed > > the scope of the one being added to only compare seccomp fds. > > > > Thoughts welcome, > > Hi, sorry I've been slow/busy. I'm finally reading through these threads. > > Happy bit: > - avoiding eBPF and just saving the original filters makes things much easier. > > Sad bit: > - inventing a new interface for seccompfds feels like massive overkill to me. > > While Andy has big dreams, we're not presently doing seccompfd > monitoring, etc. There's no driving user for that kind of interface, > and accepting the maintenance burden of it only for CRIU seems unwise. > > So, I'll go back to what I originally proposed at LSS (which it looks > like we're half way there now): > > - save the original filter (done!) > - extract filters through a single special-purpose interface (looks > like ptrace is the way to go: root-only, stopped process, etc) > - compare filter content and issue TSYNCs to merge detected sibling > threads, since merging things that weren't merged before creates no > problems. > > This means the parenting logic is heuristic, but it's entirely in > userspace, so the complexity burden doesn't live in seccomp which we, > by design, want to keep as simple as possible. Ok, how about, struct sock_filter insns[BPF_MAXINSNS]; insn_cnt = ptrace(PTRACE_SECCOMP_GET_FILTER, pid, insns, i); when asking for the ith filter? It returns either the number of instructions, -EINVAL if something was wrong (i, pid, CONFIG_CHECKPOINT_RESTORE isn't enabled). While it would always succeed now, if/when the underlying filter was not created from a bpf classic filter, we can return -EMEDIUMTYPE? (Suggestions welcome, I picked this mostly based on what sounds nice.) Tycho -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
