Messages in this thread | | | Date | Fri, 12 Jun 2015 16:55:55 -0700 | From | Alexei Starovoitov <> | Subject | Re: [PATCH net-next 1/3] bpf: introduce current->pid, tgid, uid, gid, comm accessors |
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On 6/12/15 4:47 PM, Andy Lutomirski wrote: > On Fri, Jun 12, 2015 at 4:38 PM, Alexei Starovoitov <ast@plumgrid.com> 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.
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