On Thu, 2008-09-18 at 11:09 -0700, Eric W. Biederman wrote: > Stephen Smalley <sds@xxxxxxxxxxxxx> writes: > > > On Thu, 2008-09-18 at 08:38 -0400, Stephen Smalley wrote: > >> I do however think that the mantra that we can't require users to update > >> policy for kernel changes is unsupportable in general. The precise set > >> of permission checks on a given operation is not set in stone and it is > >> not part of the kernel/userland interface/contract. Policy isn't > >> "userspace"; it governs what userspace can do, and it has to adapt to > >> kernel changes. > > > > I should note here that for changes to SELinux, we have gone out of our > > way to avoid such breakage to date through the introduction of > > compatibility switches, policy flags to enable any new checks, etc > > (albeit at a cost in complexity and ever creeping compatibility code). > > But changes to the rest of the kernel can just as easily alter the set > > of permission checks that get applied on a given operation, and I don't > > think we are always going to be able to guarantee that new kernel + old > > policy will Just Work. > > I know of at least 2 more directories that I intend to turn into > symlinks into somewhere under /proc/self. How do we keep from > breaking selinux policies when I do that? I suspect we could tweak the logic in selinux_proc_get_sid() to always label all symlinks under /proc with the base proc_t type already used for e.g. /proc/self, at which point existing policies would be ok. > For comparison how do we handle sysfs? Unresolved; presently has a single label for all nodes. See https://bugzilla.redhat.com/show_bug.cgi?id=228902 for prior discussion of fine-grained labeling support for sysfs. > How do we handle device nodes in tmpfs? udev has selinux support - looks up the appropriate context in a userland config file (file_contexts) via libselinux matchpathcon(3) and sets it upon creation. tmpfs has long supported getting/setting security.* attributes. > Ultimately do we want to implement xattrs and inotify on /proc? > Or is there another way that would simplify maintenance? If proc supported setxattr, then I suppose early userspace could label it instead of the kernel needing to determine a label internally. But not sure how we'd cleanly migrate to avoid breakage with old userspace. -- Stephen Smalley National Security Agency -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
