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]
If KCMP_FILE_PRIVATE_DATA isn't desired, I think a global counter id is the next best. -Kees -- Kees Cook Chrome OS Security -- 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
