Messages in this thread | | | From | Kees Cook <> | Date | Mon, 26 Feb 2018 16:49:21 -0800 | Subject | Re: [RFC 1/3] seccomp: add a return code to trap to userspace |
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On Wed, Feb 14, 2018 at 9:19 AM, Andy Lutomirski <luto@amacapital.net> wrote: > On Wed, Feb 14, 2018 at 3:29 PM, Tycho Andersen <tycho@tycho.ws> wrote: >> On Tue, Feb 13, 2018 at 01:09:20PM -0800, Kees Cook wrote: >>> On Sun, Feb 4, 2018 at 2:49 AM, Tycho Andersen <tycho@tycho.ws> wrote: >>> I wonder if this communication should be netlink, which gives a more >>> well-structured way to describe what's on the wire? The reason I ask >>> is because if we ever change the seccomp_data structure, we'll now >>> have two places where we need to deal with it (the first being within >>> the BPF itself). My initial idea was to prefix the communication with >>> a size field, then send the structure, and then I had nightmares, and >>> realized this was basically netlink reinvented. >> >> I suggested netlink in LA, and everyone (especially Andy) groaned very >> loudly :). I'm happy to switch it to netlink if you like, although i >> think memcpy() of structs should be safe here, since the return value >> from read or write can indicate the size of things. > > I could easily get on board with "netlink" (i.e. NLA) messages sent > over an fd. I will object strongly to the use of netlink *sockets*.
Yeah, I was thinking NLA over the fd; not a netlink socket.
>>> An ERRNO filter would block a USER_NOTIF because it's unconditional. >>> TRACE could be either, USER_NOTIF could be either. >>> >>> This means TRACE rules would be bumped by a USER_NOTIF... hmm. >> >> Yes, I didn't exactly know what to do here. ERRNO, TRAP, and KILL all >> seemed more important than USER_NOTIF, but TRACE didn't. I don't have >> a strong opinion about what to do here, because users can adjust their >> filters accordingly. Let me know what you prefer. > > If we switched to eBPF functions, this whole issue goes away.
Yeah, though we'd still need some kind of "wait for answer" eBPF function. It feels wrong to re-use maps for that...
-Kees
-- Kees Cook Pixel Security
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