From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: [PATCH net-next 1/3] bpf: introduce current->pid, tgid, uid, gid, comm accessors Date: Fri, 12 Jun 2015 16:55:55 -0700 Message-ID: <557B718B.80604@plumgrid.com> References: <1434145226-17892-1-git-send-email-ast@plumgrid.com> <1434145226-17892-2-git-send-email-ast@plumgrid.com> <557B60DB.5030200@plumgrid.com> <557B6A00.7000600@plumgrid.com> <557B6D74.2070305@plumgrid.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: netdev-owner@vger.kernel.org To: Andy Lutomirski Cc: "David S. Miller" , Ingo Molnar , Steven Rostedt , Wang Nan , Li Zefan , Daniel Wagner , Daniel Borkmann , Linux API , Network Development , "linux-kernel@vger.kernel.org" List-Id: linux-api@vger.kernel.org On 6/12/15 4:47 PM, Andy Lutomirski wrote: > On Fri, Jun 12, 2015 at 4:38 PM, Alexei Starovoitov 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.