On Fri, Jun 12, 2015 at 5:15 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: > On 6/12/15 5:03 PM, Andy Lutomirski wrote: >> >> On Fri, Jun 12, 2015 at 4:55 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> >> wrote: >>> >>> On 6/12/15 4:47 PM, Andy Lutomirski wrote: >>>> >>>> >>>> On Fri, Jun 12, 2015 at 4:38 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> >>>> wrote: >>>>> >>>>> >>>>> On 6/12/15 4:25 PM, Andy Lutomirski wrote: >>>>>> >>>>>> >>>>>> >>>>>> It's a dangerous tool. Also, shouldn't the returned uid match the >>>>>> namespace of the task that installed the probe, not the task that's >>>>>> being probed? >>>>> >>>>> >>>>> >>>>> >>>>> so leaking info to unprivileged apps is the concern? >>>>> The whole thing is for root only as you know. >>>>> The non-root is still far away. Today root needs to see the whole >>>>> kernel. That was the goal from the beginning. >>>>> >>>> >>>> This is more of a correctness issue than a security issue. ISTM using >>>> current_user_ns() in a kprobe is asking for trouble. It certainly >>>> allows any unprivilege user to show any uid it wants to the probe, >>>> which is probably not what the installer of the probe expects. >>> >>> >>> >>> probe doesn't expect anything. it doesn't make any decisions. >>> bpf is read only. it's _visibility_ into the kernel. >>> It's not used for security. >>> When we start connecting eBPF to seccomp I would agree that uid >>> handling needs to be done carefully, but we're not there yet. >>> I don't want to kill _visibility_ because in some distant future >>> bpf becomes a decision making tool in security area and >>> get_current_uid() will return numbers that shouldn't be blindly >>> used to reject/accept a user requesting something. That's far away. >>> >> >> All that is true, but the code that *installed* the bpf probe might >> get might confused when it logs that uid 0 did such-and-such when >> really some unprivileged userns root did it. > > > so what specifically you proposing? > Use from_kuid(&init_user_ns,...) instead? That seems reasonable to me. After all, you can't install one of these probes from a non-init userns. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
