On Fri, Sep 4, 2015 at 4:27 PM, Kees Cook <keesc...@chromium.org> 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] > > If KCMP_FILE_PRIVATE_DATA isn't desired, I think a global counter id > is the next best.
The problem is that you can't checkpoint and restore it. We could have a counter relative to the parent filter, though. --Andy > > -Kees > > -- > Kees Cook > Chrome OS Security -- Andy Lutomirski AMA Capital Management, LLC -- 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
