Re: [PATCH v2 bpf-next 00/21] bpf: Sysctl hook

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Mon, Mar 25, 2019 at 05:43:26PM -0700, Andrey Ignatov wrote:
> v1->v2:
> - add fs/proc/proc_sysctl.c mainteners to Cc:.

Kees, Luis,
any concerns with bpf hook in sysctl ?
Pls take a look at patch 2 where it touches fs/proc/proc_sysctl.c
This facility is for root to monitor dumb root tasks.
More detailed description below and in patches.

> The patch set introduces new BPF hook for sysctl.
> 
> It adds new program type BPF_PROG_TYPE_CGROUP_SYSCTL and attach type
> BPF_CGROUP_SYSCTL.
> 
> BPF_CGROUP_SYSCTL hook is placed before calling to sysctl's proc_handler so
> that accesses (read/write) to sysctl can be controlled for specific cgroup
> and either allowed or denied, or traced.
> 
> The hook has access to sysctl name, current sysctl value and (on write
> only) to new sysctl value via corresponding helpers. New sysctl value can
> be overridden by program. Both name and values (current/new) are
> represented as strings same way they're visible in /proc/sys/. It is up to
> program to parse these strings.
> 
> To help with parsing the most common kind of sysctl value, vector of
> integers, two new helpers are provided: bpf_strtol and bpf_strtoul with
> semantic similar to user space strtol(3) and strtoul(3).
> 
> The hook also provides bpf_sysctl context with two fields:
> * @write indicates whether sysctl is being read (= 0) or written (= 1);
> * @file_pos is sysctl file position to read from or write to, can be
>   overridden.
> 
> The hook allows to make better isolation for containerized applications
> that are run as root so that one container can't change a sysctl and affect
> all other containers on a host, make changes to allowed sysctl in a safer
> way and simplify sysctl tracing for cgroups.
> 
> Patch 1 is preliminary refactoring.
> Patch 2 adds new program and attach types.
> Patches 3-5 implement helpers to access sysctl name and value.
> Patch 6 adds file_pos field to bpf_sysctl context.
> Patch 7 updates UAPI in tools.
> Patches 8-9 add support for the new hook to libbpf and corresponding test.
> Patches 10-14 add selftests for the new hook.
> Patch 15 adds support for new arg types to verifier: pointer to integer.
> Patch 16 adds bpf_strto{l,ul} helpers to parse integers from sysctl value.
> Patch 17 updates UAPI in tools.
> Patch 18 updates bpf_helpers.h.
> Patch 19 adds selftests for pointer to integer in verifier.
> Patches 20-21 add selftests for bpf_strto{l,ul}, including integration
>               C based test for sysctl value parsing.
> 
> 
> Andrey Ignatov (21):
>   bpf: Add base proto function for cgroup-bpf programs
>   bpf: Sysctl hook
>   bpf: Introduce bpf_sysctl_get_name helper
>   bpf: Introduce bpf_sysctl_get_current_value helper
>   bpf: Introduce bpf_sysctl_{get,set}_new_value helpers
>   bpf: Add file_pos field to bpf_sysctl ctx
>   bpf: Sync bpf.h to tools/
>   libbpf: Support sysctl hook
>   selftests/bpf: Test sysctl section name
>   selftests/bpf: Test BPF_CGROUP_SYSCTL
>   selftests/bpf: Test bpf_sysctl_get_name helper
>   selftests/bpf: Test sysctl_get_current_value helper
>   selftests/bpf: Test bpf_sysctl_{get,set}_new_value helpers
>   selftests/bpf: Test file_pos field in bpf_sysctl ctx
>   bpf: Introduce ARG_PTR_TO_{INT,LONG} arg types
>   bpf: Introduce bpf_strtol and bpf_strtoul helpers
>   bpf: Sync bpf.h to tools/
>   selftests/bpf: Add sysctl and strtoX helpers to bpf_helpers.h
>   selftests/bpf: Test ARG_PTR_TO_LONG arg type
>   selftests/bpf: Test bpf_strtol and bpf_strtoul helpers
>   selftests/bpf: C based test for sysctl and strtoX
> 
>  fs/proc/proc_sysctl.c                         |   25 +-
>  include/linux/bpf-cgroup.h                    |   21 +
>  include/linux/bpf.h                           |    4 +
>  include/linux/bpf_types.h                     |    1 +
>  include/linux/filter.h                        |   16 +
>  include/uapi/linux/bpf.h                      |  139 +-
>  kernel/bpf/cgroup.c                           |  364 +++-
>  kernel/bpf/helpers.c                          |  131 ++
>  kernel/bpf/syscall.c                          |    7 +
>  kernel/bpf/verifier.c                         |   30 +
>  tools/include/uapi/linux/bpf.h                |  139 +-
>  tools/lib/bpf/libbpf.c                        |    3 +
>  tools/lib/bpf/libbpf_probes.c                 |    1 +
>  tools/testing/selftests/bpf/Makefile          |    3 +-
>  tools/testing/selftests/bpf/bpf_helpers.h     |   19 +
>  .../selftests/bpf/progs/test_sysctl_prog.c    |   89 +
>  .../selftests/bpf/test_section_names.c        |    5 +
>  tools/testing/selftests/bpf/test_sysctl.c     | 1567 +++++++++++++++++
>  .../testing/selftests/bpf/verifier/int_ptr.c  |  160 ++
>  19 files changed, 2716 insertions(+), 8 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/progs/test_sysctl_prog.c
>  create mode 100644 tools/testing/selftests/bpf/test_sysctl.c
>  create mode 100644 tools/testing/selftests/bpf/verifier/int_ptr.c
> 
> -- 
> 2.17.1
>