On Thu, May 20, 2021 at 10:56:13AM +0200, Christian Brauner wrote: > On Thu, May 20, 2021 at 03:16:10AM -0500, Tianyin Xu wrote: > > On Mon, May 17, 2021 at 10:40 AM Tycho Andersen <tycho@tycho.pizza> wrote: > > > > > > On Sun, May 16, 2021 at 03:38:00AM -0500, Tianyin Xu wrote: > > > > On Sat, May 15, 2021 at 10:49 AM Andy Lutomirski <luto@xxxxxxxxxx> wrote: > > > > > > > > > > On 5/10/21 10:21 PM, YiFei Zhu wrote: > > > > > > On Mon, May 10, 2021 at 12:47 PM Andy Lutomirski <luto@xxxxxxxxxx> wrote: > > > > > >> On Mon, May 10, 2021 at 10:22 AM YiFei Zhu <zhuyifei1999@xxxxxxxxx> wrote: > > > > > >>> > > > > > >>> From: YiFei Zhu <yifeifz2@xxxxxxxxxxxx> > > > > > >>> > > > > > >>> Based on: https://urldefense.com/v3/__https://lists.linux-foundation.org/pipermail/containers/2018-February/038571.html__;!!DZ3fjg!thbAoRgmCeWjlv0qPDndNZW1j6Y2Kl_huVyUffr4wVbISf-aUiULaWHwkKJrNJyo$ > > > > > >>> > > > > > >>> This patchset enables seccomp filters to be written in eBPF. Before I dive in, I do want to say that this is very interesting work. Thanks for working on it, even if we're all so grumpy about accepting it. :) > > > > > >>> Supporting eBPF filters has been proposed a few times in the past. > > > > > >>> The main concerns were (1) use cases and (2) security. We have > > > > > >>> identified many use cases that can benefit from advanced eBPF > > > > > >>> filters, such as: > > > > > >> > > > > > >> I haven't reviewed this carefully, but I think we need to distinguish > > > > > >> a few things: > > > > > >> > > > > > >> 1. Using the eBPF *language*. Likely everyone is aware, but I'll point out for anyone new reading this thread: seccomp uses eBPF under the hood: all the cBPF is transformed to eBPF at filter attach time. But yes, I get the point: using the _entire_ eBPF language. Though I'd remind folks that seccomp doesn't even use the entire cBPF language... > [...] but Andy's point stands that this brings a slew of issues on > the table that need clear answers. Bringing stateful ebpf features into > seccomp is a pretty big step and especially around the > privilege/security model it looks pretty handwavy right now. This is the blocker as far as I'm concerned: there is no story for unprivileged eBPF. And even IF there was a story there, I find the rate of security-related flaws in eBPF to be way too high for a sandboxing primitive to depend on. There have been around a dozen a year for the last 4 years: $ git log --oneline --no-merges --pretty=format:'%as %h %s' \ -i -E \ --all-match --grep '^Fixes:' --grep \ '(over|under)flow|\bleak|escalat|expos(e[ds]?|ure)\b|use[- ]?after[- ]?free' \ -- kernel/bpf/ | cut -d- -f1 | sort | uniq -c 4 2015 4 2016 13 2017 16 2018 18 2019 12 2020 6 2021 I just can't bring myself to accept that level of risk for seccomp. (And yes, this might be mitigated by blocking the bpf() syscall within a filter, but then eBPF seccomp would become kind of useless inside a container launcher, etc etc.) -Kees -- Kees Cook
