Messages in this thread | | | Date | Mon, 27 Mar 2023 10:28:27 -0700 | Subject | Re: [RFC PATCH bpf-next 00/13] bpf: Introduce BPF namespace | From | Stanislav Fomichev <> |
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On 03/26, Yafang Shao wrote: > Currently only CAP_SYS_ADMIN can iterate BPF object IDs and convert IDs > to FDs, that's intended for BPF's security model[1]. Not only does it > prevent non-privilidged users from getting other users' bpf program, but > also it prevents the user from iterating his own bpf objects.
> In container environment, some users want to run bpf programs in their > containers. These users can run their bpf programs under CAP_BPF and > some other specific CAPs, but they can't inspect their bpf programs in a > generic way. For example, the bpftool can't be used as it requires > CAP_SYS_ADMIN. That is very inconvenient.
> Without CAP_SYS_ADMIN, the only way to get the information of a bpf object > which is not created by the process itself is with SCM_RIGHTS, that > requires each processes which created bpf object has to implement a unix > domain socket to share the fd of a bpf object between different > processes, that is really trivial and troublesome.
> Hence we need a better mechanism to get bpf object info without > CAP_SYS_ADMIN.
[..]
> BPF namespace is introduced in this patchset with an attempt to remove > the CAP_SYS_ADMIN requirement. The user can create bpf map, prog and > link in a specific bpf namespace, then these bpf objects will not be > visible to the users in a different bpf namespace. But these bpf > objects are visible to its parent bpf namespace, so the sys admin can > still iterate and inspect them.
Does it essentially mean unpriv bpf? Can I, as a non-root, create a new bpf namespace and start loading/attaching progs? Maybe add a paragraph about now vs whatever you're proposing. Otherwise it's not very clear what's the security story. (haven't looked at the whole series, so maybe it's answered somewhere else?)
> BPF namespace is similar to PID namespace, and the bpf objects are > similar to tasks, so BPF namespace is very easy to understand. These > patchset only implements BPF namespace for bpf map, prog and link. In the > future we may extend it to other bpf objects like btf, bpffs and etc. > For example, we can allow some of the BTF objects to be used in > non-init bpf namespace, then the container user can only trace the > processes running in his container, but can't get the information of > tasks running in other containers.
> A simple example is introduced into selftests/bpf on how to use the bpf > namespace.
> Putting bpf map, prog and link into bpf namespace is the first step. > Let's start with it.
> [1]. > https://lore.kernel.org/bpf/20200513230355.7858-1-alexei.starovoitov@gmail.com/
> Yafang Shao (13): > fork: New clone3 flag for BPF namespace > proc_ns: Extend the field type in struct proc_ns_operations to long > bpf: Implement bpf namespace > bpf: No need to check if id is 0 > bpf: Make bpf objects id have the same alloc and free pattern > bpf: Helpers to alloc and free object id in bpf namespace > bpf: Add bpf helper to get bpf object id > bpf: Alloc and free bpf_map id in bpf namespace > bpf: Alloc and free bpf_prog id in bpf namespace > bpf: Alloc and free bpf_link id in bpf namespace > bpf: Allow iterating bpf objects with CAP_BPF in bpf namespace > bpf: Use bpf_idr_lock array instead > selftests/bpf: Add selftest for bpf namespace
> fs/proc/namespaces.c | 4 + > include/linux/bpf.h | 9 +- > include/linux/bpf_namespace.h | 88 ++++++++++ > include/linux/nsproxy.h | 4 + > include/linux/proc_ns.h | 3 +- > include/linux/user_namespace.h | 1 + > include/uapi/linux/bpf.h | 7 + > include/uapi/linux/sched.h | 1 + > kernel/bpf/Makefile | 1 + > kernel/bpf/bpf_namespace.c | 283 > ++++++++++++++++++++++++++++++ > kernel/bpf/offload.c | 16 +- > kernel/bpf/syscall.c | 262 > ++++++++++----------------- > kernel/bpf/task_iter.c | 12 ++ > kernel/fork.c | 5 +- > kernel/nsproxy.c | 19 +- > kernel/trace/bpf_trace.c | 2 + > kernel/ucount.c | 1 + > tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 13 +- > tools/include/uapi/linux/bpf.h | 7 + > tools/testing/selftests/bpf/Makefile | 3 +- > tools/testing/selftests/bpf/test_bpfns.c | 76 ++++++++ > 21 files changed, 637 insertions(+), 180 deletions(-) > create mode 100644 include/linux/bpf_namespace.h > create mode 100644 kernel/bpf/bpf_namespace.c > create mode 100644 tools/testing/selftests/bpf/test_bpfns.c
> -- > 1.8.3.1
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