From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70855C433EF for ; Mon, 11 Apr 2022 18:46:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349236AbiDKSss (ORCPT ); Mon, 11 Apr 2022 14:48:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231283AbiDKSsr (ORCPT ); Mon, 11 Apr 2022 14:48:47 -0400 Received: from mail-qk1-x734.google.com (mail-qk1-x734.google.com [IPv6:2607:f8b0:4864:20::734]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 583A21FCDB for ; Mon, 11 Apr 2022 11:46:32 -0700 (PDT) Received: by mail-qk1-x734.google.com with SMTP id c1so221604qkf.13 for ; Mon, 11 Apr 2022 11:46:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=91Li9XU9gpsJ9k8wCFOCx1n06URSq0VVBp27IbgO0dU=; b=ZE3jzHxvrXCeyfU3Ym1d86TePHiIgNaCYyP4+rQ9CLUlbAHm4ms3tb2AIilc/amm1J NdcDHNQQzHMmT/jA0Kk7+g0EJnptw9ayPbM6qU6e6z98YNRwKWtQ9WxtvQ+1BQGEKaqW 0lZhkMlBE6OaMK/0TiP5qzJkkzYgIrSKB5Yx5epoa8GDHW16j1uXNYfZNckrWC3dyuxV 8g6y2hquS/Zfm0hL2SOT6/6ntDG8YIJt+rSmkwhd+9pKeJh1jPTBPCD8Hfb40JwlabOS ZV+/aEpKWS5IWSvzn4T9/2mHSk/dRmNC7SrlmJaDuhBFXdHOiJuTguDUeIClkewxwr10 YOEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=91Li9XU9gpsJ9k8wCFOCx1n06URSq0VVBp27IbgO0dU=; b=2K9DOubFaEbhwVsAhKa2irVPYvZgyrfj/TYhN6XgHnlyFhJHPVUM7oxJ+3ZKdmDKjM OpK4ZXi9JBTZtqs2y4Ooh2VDErkparqkqXOQy2z6VmmNQSrZtN/wWM2NPoTza8lCxfKQ P93TvBMWdYx0BqOc1o63j69Pd62TXYMdnn2C2JfajdWTEhAjwpSHyk+aGyCrLKUgmnUz yilw6CtsXg8Hb/6+QKZAkSydBfGdNluZxVSryzZkF/fJLjHwvZguEfi89rErYRxO5pqE Huss74WU4tVbA1hAT5sXQfSGIe5dGBWw3ROaCVdmlDPPW1rI0c0qmGnTHXg7LPp+9zBq kNzw== X-Gm-Message-State: AOAM530pevI5xO4Kc8QRPCKPG37IqOkUzEwiEjMWs8UtZuf3XjatAg0l lZHt4O3HMIgNeSYW2kp8On2gnxUa0IqIt8IuQje4Lw== X-Google-Smtp-Source: ABdhPJxPt6k2TunyH0GsmTgJkWGdFloK65fX+MIrLpDEF9/p39z+AURPMKD9fLQujeyYFeRlXPPe6i8pbLZMBWvs+U8= X-Received: by 2002:ae9:eb01:0:b0:69c:10ca:ed6 with SMTP id b1-20020ae9eb01000000b0069c10ca0ed6mr574203qkg.496.1649702791220; Mon, 11 Apr 2022 11:46:31 -0700 (PDT) MIME-Version: 1.0 References: <20220407223112.1204582-1-sdf@google.com> <20220407223112.1204582-4-sdf@google.com> <20220408225628.oog4a3qteauhqkdn@kafai-mbp.dhcp.thefacebook.com> In-Reply-To: <20220408225628.oog4a3qteauhqkdn@kafai-mbp.dhcp.thefacebook.com> From: Stanislav Fomichev Date: Mon, 11 Apr 2022 11:46:20 -0700 Message-ID: Subject: Re: [PATCH bpf-next v3 3/7] bpf: minimize number of allocated lsm slots per program To: Martin KaFai Lau Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Apr 8, 2022 at 3:57 PM Martin KaFai Lau wrote: > > On Thu, Apr 07, 2022 at 03:31:08PM -0700, Stanislav Fomichev wrote: > > Previous patch adds 1:1 mapping between all 211 LSM hooks > > and bpf_cgroup program array. Instead of reserving a slot per > > possible hook, reserve 10 slots per cgroup for lsm programs. > > Those slots are dynamically allocated on demand and reclaimed. > > This still adds some bloat to the cgroup and brings us back to > > roughly pre-cgroup_bpf_attach_type times. > > > > It should be possible to eventually extend this idea to all hooks if > > the memory consumption is unacceptable and shrink overall effective > > programs array. > > > > Signed-off-by: Stanislav Fomichev > > --- > > include/linux/bpf-cgroup-defs.h | 4 +- > > include/linux/bpf_lsm.h | 6 --- > > kernel/bpf/bpf_lsm.c | 9 ++-- > > kernel/bpf/cgroup.c | 96 ++++++++++++++++++++++++++++----- > > 4 files changed, 90 insertions(+), 25 deletions(-) > > > > diff --git a/include/linux/bpf-cgroup-defs.h b/include/linux/bpf-cgroup-defs.h > > index 6c661b4df9fa..d42516e86b3a 100644 > > --- a/include/linux/bpf-cgroup-defs.h > > +++ b/include/linux/bpf-cgroup-defs.h > > @@ -10,7 +10,9 @@ > > > > struct bpf_prog_array; > > > > -#define CGROUP_LSM_NUM 211 /* will be addressed in the next patch */ > > +/* Maximum number of concurrently attachable per-cgroup LSM hooks. > > + */ > > +#define CGROUP_LSM_NUM 10 > hmm...only 10 different lsm hooks (or 10 different attach_btf_ids) can > have BPF_LSM_CGROUP programs attached. This feels quite limited but having > a static 211 (and potentially growing in the future) is not good either. > I currently do not have a better idea also. :/ > > Have you thought about other dynamic schemes or they would be too slow ? > > > enum cgroup_bpf_attach_type { > > CGROUP_BPF_ATTACH_TYPE_INVALID = -1, > > diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h > > index 7f0e59f5f9be..613de44aa429 100644 > > --- a/include/linux/bpf_lsm.h > > +++ b/include/linux/bpf_lsm.h > > @@ -43,7 +43,6 @@ extern const struct bpf_func_proto bpf_inode_storage_delete_proto; > > void bpf_inode_storage_free(struct inode *inode); > > > > int bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func); > > -int bpf_lsm_hook_idx(u32 btf_id); > > > > #else /* !CONFIG_BPF_LSM */ > > > > @@ -74,11 +73,6 @@ static inline int bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, > > return -ENOENT; > > } > > > > -static inline int bpf_lsm_hook_idx(u32 btf_id) > > -{ > > - return -EINVAL; > > -} > > - > > #endif /* CONFIG_BPF_LSM */ > > > > #endif /* _LINUX_BPF_LSM_H */ > > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c > > index eca258ba71d8..8b948ec9ab73 100644 > > --- a/kernel/bpf/bpf_lsm.c > > +++ b/kernel/bpf/bpf_lsm.c > > @@ -57,10 +57,12 @@ static unsigned int __cgroup_bpf_run_lsm_socket(const void *ctx, > > if (unlikely(!sk)) > > return 0; > > > > + rcu_read_lock(); /* See bpf_lsm_attach_type_get(). */ > > cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data); > > if (likely(cgrp)) > > ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[prog->aux->cgroup_atype], > > ctx, bpf_prog_run, 0); > > + rcu_read_unlock(); > > return ret; > > } > > > > @@ -77,7 +79,7 @@ static unsigned int __cgroup_bpf_run_lsm_current(const void *ctx, > > /*prog = container_of(insn, struct bpf_prog, insnsi);*/ > > prog = (const struct bpf_prog *)((void *)insn - offsetof(struct bpf_prog, insnsi)); > > > > - rcu_read_lock(); > > + rcu_read_lock(); /* See bpf_lsm_attach_type_get(). */ > I think this is also needed for task_dfl_cgroup(). If yes, > will be a good idea to adjust the comment if it ends up > using the 'CGROUP_LSM_NUM 10' scheme. > > While at rcu_read_lock(), have you thought about what major things are > needed to make BPF_LSM_CGROUP sleepable ? > > The cgroup local storage could be one that require changes but it seems > the cgroup local storage is not available to BPF_LSM_GROUP in this change set. > The current use case doesn't need it? No, I haven't thought about sleepable at all yet :-( But seems like having that rcu lock here might be problematic if we want to sleep? In this case, Jakub's suggestion seems better.