On Wed, Sep 9, 2015 at 3:34 PM, Tycho Andersen <tycho.ander...@canonical.com> wrote: > On Fri, Sep 04, 2015 at 06:27:27PM -0600, Tycho Andersen wrote: >> On Fri, Sep 04, 2015 at 04:08:53PM -0700, Andy Lutomirski wrote: >> > On Fri, Sep 4, 2015 at 3:28 PM, Tycho Andersen >> > <tycho.ander...@canonical.com> wrote: >> > > On Fri, Sep 04, 2015 at 02:48:03PM -0700, Andy Lutomirski wrote: >> > >> On Fri, Sep 4, 2015 at 1:45 PM, Tycho Andersen >> > >> <tycho.ander...@canonical.com> wrote: >> > >> > On Fri, Sep 04, 2015 at 01:17:30PM -0700, Kees Cook wrote: >> > >> >> On Fri, Sep 4, 2015 at 9:04 AM, Tycho Andersen >> > >> >> <tycho.ander...@canonical.com> wrote: >> > >> >> > This commit adds a way to dump eBPF programs. The initial >> > >> >> > implementation >> > >> >> > doesn't support maps, and therefore only allows dumping seccomp >> > >> >> > ebpf >> > >> >> > programs which themselves don't currently support maps. >> > >> >> > >> > >> >> > We export the GPL bit as well as a unique ID for the program so >> > >> >> > that >> > >> >> >> > >> >> This unique ID appears to be the heap address for the prog. That's a >> > >> >> huge leak, and should not be done. We don't want to introduce new >> > >> >> kernel address leaks while we're trying to fix the remaining ones. >> > >> >> Shouldn't the "unique ID" be the fd itself? I imagine KCMP_FILE >> > >> >> could be used, for example. >> > >> > >> > >> > No; we acquire the fd per process, so if a task installs a filter and >> > >> > then forks N times, we'll grab N (+1) copies of the filter from N (+1) >> > >> > different file descriptors. Ideally, we'd have some way to figure out >> > >> > that these were all the same. Some sort of prog_id is one way, >> > >> > although there may be others. >> > >> >> > >> I disagree a bit. I think we want the actual hierarchy to be a >> > >> well-defined thing, because I have plans to make the hierarchy >> > >> actually do something. That means that we'll need to have a more >> > >> exact way to dump the hierarchy than "these two filters are identical" >> > >> or "these two filters are not identical". >> > > >> > > Can you elaborate on what this would look like? I think with the >> > > "these two filters are the same" primitive (the same in the sense that >> > > they were inherited during a fork, not just that >> > > memcmp(filter1->insns, filter2->insns) == 0) you can infer the entire >> > > hierarchy, however clunky it may be to do so. >> > > >> > > Another issue is that KCMP_FILE won't work in this case, as it >> > > effectively compares the struct file *, which will be different since >> > > we need to call anon_inode_getfd() for each call of >> > > ptrace(PTRACE_SECCOMP_GET_FILTER_FD). We could add a KCMP_BPF (or just >> > > a KCMP_FILE_PRIVATE_DATA, since that's effectively what it would be). >> > > Does that make sense? [added Cyrill] >> > > >> > >> > I don't really know what it would look like. I think we want a way to >> > compare struct seccomp_filter pointers. > > Here's a thought, > > The set I'm currently proposing effectively separates the ref-counting > of the struct seccomp_filter from the struct bpf_prog (by necessity, > since we're referring to filters from fds). What if we went a little > futher, and made a copy of each seccomp_filter on fork(), keeping it > pointed at the same bpf_prog but adding some metadata about how it was > inherited (tsk->seccomp.filter->inheritence_count++ perhaps). This > would still require this change:
Won't that break the tsync mechanism? --Andy -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
