Re: [PATCH bpf-next v8 03/11] bpf: per-cgroup lsm flavor

[Stanislav Fomichev <sdf@google.com>]

On Wed, Jun 1, 2022 at 11:17 PM kernel test robot <lkp@intel.com> wrote:
>
> Hi Stanislav,
>
> Thank you for the patch! Perhaps something to improve:

This is a config without CONFIG_BPF_LSM and it makes CGROUP_LSM_START
greater than CGROUP_LSM_END (to make sure we don't
waste slots on non-CONFIG_BPF_LSM builds) and it screws up
(atype >= CGROUP_LSM_START && atype <= CGROUP_LSM_END) check.
I'll add an ifdef around that.


> [auto build test WARNING on bpf-next/master]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Stanislav-Fomichev/bpf-cgroup_sock-lsm-flavor/20220602-050600
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
> config: i386-randconfig-a004 (https://download.01.org/0day-ci/archive/20220602/202206021403.M9hFZdbY-lkp@intel.com/config)
> compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project b364c76683f8ef241025a9556300778c07b590c2)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://github.com/intel-lab-lkp/linux/commit/584b25fdd30894c312d577f4b6b83f93d64e464b
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Stanislav-Fomichev/bpf-cgroup_sock-lsm-flavor/20220602-050600
>         git checkout 584b25fdd30894c312d577f4b6b83f93d64e464b
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/bpf/
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> >> kernel/bpf/cgroup.c:257:35: warning: overlapping comparisons always evaluate to false [-Wtautological-overlap-compare]
>                                    if (atype >= CGROUP_LSM_START && atype <= CGROUP_LSM_END)
>                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
>    kernel/bpf/cgroup.c:252:35: warning: overlapping comparisons always evaluate to false [-Wtautological-overlap-compare]
>                                    if (atype >= CGROUP_LSM_START && atype <= CGROUP_LSM_END)
>                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
>    2 warnings generated.
>
>
> vim +257 kernel/bpf/cgroup.c
>
>    226
>    227  /**
>    228   * cgroup_bpf_release() - put references of all bpf programs and
>    229   *                        release all cgroup bpf data
>    230   * @work: work structure embedded into the cgroup to modify
>    231   */
>    232  static void cgroup_bpf_release(struct work_struct *work)
>    233  {
>    234          struct cgroup *p, *cgrp = container_of(work, struct cgroup,
>    235                                                 bpf.release_work);
>    236          struct bpf_prog_array *old_array;
>    237          struct list_head *storages = &cgrp->bpf.storages;
>    238          struct bpf_cgroup_storage *storage, *stmp;
>    239
>    240          unsigned int atype;
>    241
>    242          mutex_lock(&cgroup_mutex);
>    243
>    244          for (atype = 0; atype < ARRAY_SIZE(cgrp->bpf.progs); atype++) {
>    245                  struct hlist_head *progs = &cgrp->bpf.progs[atype];
>    246                  struct bpf_prog_list *pl;
>    247                  struct hlist_node *pltmp;
>    248
>    249                  hlist_for_each_entry_safe(pl, pltmp, progs, node) {
>    250                          hlist_del(&pl->node);
>    251                          if (pl->prog) {
>    252                                  if (atype >= CGROUP_LSM_START && atype <= CGROUP_LSM_END)
>    253                                          bpf_trampoline_unlink_cgroup_shim(pl->prog);
>    254                                  bpf_prog_put(pl->prog);
>    255                          }
>    256                          if (pl->link) {
>  > 257                                  if (atype >= CGROUP_LSM_START && atype <= CGROUP_LSM_END)
>    258                                          bpf_trampoline_unlink_cgroup_shim(pl->link->link.prog);
>    259                                  bpf_cgroup_link_auto_detach(pl->link);
>    260                          }
>    261                          kfree(pl);
>    262                          static_branch_dec(&cgroup_bpf_enabled_key[atype]);
>    263                  }
>    264                  old_array = rcu_dereference_protected(
>    265                                  cgrp->bpf.effective[atype],
>    266                                  lockdep_is_held(&cgroup_mutex));
>    267                  bpf_prog_array_free(old_array);
>    268          }
>    269
>    270          list_for_each_entry_safe(storage, stmp, storages, list_cg) {
>    271                  bpf_cgroup_storage_unlink(storage);
>    272                  bpf_cgroup_storage_free(storage);
>    273          }
>    274
>    275          mutex_unlock(&cgroup_mutex);
>    276
>    277          for (p = cgroup_parent(cgrp); p; p = cgroup_parent(p))
>    278                  cgroup_bpf_put(p);
>    279
>    280          percpu_ref_exit(&cgrp->bpf.refcnt);
>    281          cgroup_put(cgrp);
>    282  }
>    283
>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp