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. Also, as you start calling more and more non-trivial functions from bpf, you might need to start preventing bpf probe installations in those functions. --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
