From patchwork Wed Oct 11 12:08:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuyi Zhou X-Patchwork-Id: 13417278 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 684FA1EA97 for ; Wed, 11 Oct 2023 12:10:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="HNYpW+UB" Received: from mail-pf1-x42b.google.com (mail-pf1-x42b.google.com [IPv6:2607:f8b0:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3AE77D5C for ; Wed, 11 Oct 2023 05:09:44 -0700 (PDT) Received: by mail-pf1-x42b.google.com with SMTP id d2e1a72fcca58-690bc3f82a7so5220404b3a.0 for ; Wed, 11 Oct 2023 05:09:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1697026172; x=1697630972; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=spK2veKjGKPWlL695PFbHPuUiEqdtYJXw3T2DQ3u9LI=; b=HNYpW+UBrqt1EsgOIjp8OlgFt+mMZYusVSuqLV+l/QNLFNSyFc8wDu52pcMSXvk8aN NTmBSuhCYHw1X6T7563JgBBENauR1pagGauCpBDUSWy5DcN6RR0aDrw36Lub/A3yU5jD wToRVraUczoB+pltLxsW56ixxIdV4uskoeyaIYSxmXCglA3hK0/TLBWcZHgNY9+P2tTX ODstqAamlpifAG4ZTg1TyS3WCouQytiQQg4UlBjsPQp3XA3fx3ncHvUSZXxybeTYlXD0 JaSwiC6P8aB09giMMPD64moeHD+fROMg1vMnNCwDVG4Dgis5ff/x1hhndpkqaE7XQcoC b18A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697026172; x=1697630972; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=spK2veKjGKPWlL695PFbHPuUiEqdtYJXw3T2DQ3u9LI=; b=BwcVmyIMq+qzpf4jSMbF13y41F+NQs51p0i5V5D8RsBtBZeN+2bDDbx3AAqlSa51Eq oLOzK9G3OtjOXIpW2uP7I7HlDFxXZBSx5DXFb8b1pmSk1OL5O6KdqopeZxZmNLEUKu2K FpyT99PxDgAV1KMlFL+K3MdkiQ/2LG5E9N7pJPv0tSbOvxv8DSA+RafiVB2FdQvAwf67 WJEGbt4l4Y1ON8j25i/zpKT7oN4NhA8DGAjVQ0HgEUxxA4h1EHKtYpAF6oqrZnA0nh8R TdNTNYTcxNVSeW7GAcJiUXph6KpSUAo03kOiOZ+BdieugH3BvVqFi+lWoL00vZ9PGLZr S3vA== X-Gm-Message-State: AOJu0YwFmQWULp0K5Q4tWGzw/vt2IpcC4aWrz94Vfdd3uwFXKnZlyavU PouyOdJGwgJ+ZnhVyF4BZDvkpj/xLg+LMHe8rGI= X-Google-Smtp-Source: AGHT+IFTklTZEuAxwA2HhEfukzlMTtmRC5V7W2fvftjRg7l7SsdYyrLWWuTwN/rd6UUqNMUvMxcl4w== X-Received: by 2002:a05:6a00:1943:b0:690:d4fa:d43d with SMTP id s3-20020a056a00194300b00690d4fad43dmr18270745pfk.6.1697026171738; Wed, 11 Oct 2023 05:09:31 -0700 (PDT) Received: from n37-019-243.byted.org ([180.184.51.142]) by smtp.gmail.com with ESMTPSA id u13-20020a62ed0d000000b006930db1e6cfsm9962769pfh.62.2023.10.11.05.09.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Oct 2023 05:09:31 -0700 (PDT) From: Chuyi Zhou To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, tj@kernel.org, linux-kernel@vger.kernel.org, Chuyi Zhou Subject: [PATCH bpf-next v5 5/8] bpf: teach the verifier to enforce css_iter and task_iter in RCU CS Date: Wed, 11 Oct 2023 20:08:54 +0800 Message-Id: <20231011120857.251943-6-zhouchuyi@bytedance.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20231011120857.251943-1-zhouchuyi@bytedance.com> References: <20231011120857.251943-1-zhouchuyi@bytedance.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net css_iter and task_iter should be used in rcu section. Specifically, in sleepable progs explicit bpf_rcu_read_lock() is needed before use these iters. In normal bpf progs that have implicit rcu_read_lock(), it's OK to use them directly. This patch adds a new a KF flag KF_RCU_PROTECTED for bpf_iter_task_new and bpf_iter_css_new. It means the kfunc should be used in RCU CS. We check whether we are in rcu cs before we want to invoke this kfunc. If the rcu protection is guaranteed, we would let st->type = PTR_TO_STACK | MEM_RCU. Once user do rcu_unlock during the iteration, state MEM_RCU of regs would be cleared. is_iter_reg_valid_init() will reject if reg->type is UNTRUSTED. It is worth noting that currently, bpf_rcu_read_unlock does not clear the state of the STACK_ITER reg, since bpf_for_each_spilled_reg only considers STACK_SPILL. This patch also let bpf_for_each_spilled_reg search STACK_ITER. Signed-off-by: Chuyi Zhou Acked-by: Andrii Nakryiko --- include/linux/bpf_verifier.h | 19 ++++++++------ include/linux/btf.h | 1 + kernel/bpf/helpers.c | 4 +-- kernel/bpf/verifier.c | 50 ++++++++++++++++++++++++++++-------- 4 files changed, 53 insertions(+), 21 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 94ec766432f5..e67cd45a85be 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -386,19 +386,18 @@ struct bpf_verifier_state { u32 jmp_history_cnt; }; -#define bpf_get_spilled_reg(slot, frame) \ +#define bpf_get_spilled_reg(slot, frame, mask) \ (((slot < frame->allocated_stack / BPF_REG_SIZE) && \ - (frame->stack[slot].slot_type[0] == STACK_SPILL)) \ + ((1 << frame->stack[slot].slot_type[0]) & (mask))) \ ? &frame->stack[slot].spilled_ptr : NULL) /* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */ -#define bpf_for_each_spilled_reg(iter, frame, reg) \ - for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \ +#define bpf_for_each_spilled_reg(iter, frame, reg, mask) \ + for (iter = 0, reg = bpf_get_spilled_reg(iter, frame, mask); \ iter < frame->allocated_stack / BPF_REG_SIZE; \ - iter++, reg = bpf_get_spilled_reg(iter, frame)) + iter++, reg = bpf_get_spilled_reg(iter, frame, mask)) -/* Invoke __expr over regsiters in __vst, setting __state and __reg */ -#define bpf_for_each_reg_in_vstate(__vst, __state, __reg, __expr) \ +#define bpf_for_each_reg_in_vstate_mask(__vst, __state, __reg, __mask, __expr) \ ({ \ struct bpf_verifier_state *___vstate = __vst; \ int ___i, ___j; \ @@ -410,7 +409,7 @@ struct bpf_verifier_state { __reg = &___regs[___j]; \ (void)(__expr); \ } \ - bpf_for_each_spilled_reg(___j, __state, __reg) { \ + bpf_for_each_spilled_reg(___j, __state, __reg, __mask) { \ if (!__reg) \ continue; \ (void)(__expr); \ @@ -418,6 +417,10 @@ struct bpf_verifier_state { } \ }) +/* Invoke __expr over regsiters in __vst, setting __state and __reg */ +#define bpf_for_each_reg_in_vstate(__vst, __state, __reg, __expr) \ + bpf_for_each_reg_in_vstate_mask(__vst, __state, __reg, 1 << STACK_SPILL, __expr) + /* linked list of verifier states used to prune search */ struct bpf_verifier_state_list { struct bpf_verifier_state state; diff --git a/include/linux/btf.h b/include/linux/btf.h index 928113a80a95..c2231c64d60b 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -74,6 +74,7 @@ #define KF_ITER_NEW (1 << 8) /* kfunc implements BPF iter constructor */ #define KF_ITER_NEXT (1 << 9) /* kfunc implements BPF iter next method */ #define KF_ITER_DESTROY (1 << 10) /* kfunc implements BPF iter destructor */ +#define KF_RCU_PROTECTED (1 << 11) /* kfunc should be protected by rcu cs when they are invoked */ /* * Tag marking a kernel function as a kfunc. This is meant to minimize the diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 6330e37ca8d5..5081a4ac5b6d 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2555,10 +2555,10 @@ BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY) BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY) -BTF_ID_FLAGS(func, bpf_iter_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_iter_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS | KF_RCU_PROTECTED) BTF_ID_FLAGS(func, bpf_iter_task_next, KF_ITER_NEXT | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_task_destroy, KF_ITER_DESTROY) -BTF_ID_FLAGS(func, bpf_iter_css_new, KF_ITER_NEW | KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_iter_css_new, KF_ITER_NEW | KF_TRUSTED_ARGS | KF_RCU_PROTECTED) BTF_ID_FLAGS(func, bpf_iter_css_next, KF_ITER_NEXT | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_css_destroy, KF_ITER_DESTROY) BTF_ID_FLAGS(func, bpf_dynptr_adjust) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 528d375c17ee..3a60cc87520e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1173,7 +1173,12 @@ static bool is_dynptr_type_expected(struct bpf_verifier_env *env, struct bpf_reg static void __mark_reg_known_zero(struct bpf_reg_state *reg); +static bool in_rcu_cs(struct bpf_verifier_env *env); + +static bool is_kfunc_rcu_protected(struct bpf_kfunc_call_arg_meta *meta); + static int mark_stack_slots_iter(struct bpf_verifier_env *env, + struct bpf_kfunc_call_arg_meta *meta, struct bpf_reg_state *reg, int insn_idx, struct btf *btf, u32 btf_id, int nr_slots) { @@ -1194,6 +1199,12 @@ static int mark_stack_slots_iter(struct bpf_verifier_env *env, __mark_reg_known_zero(st); st->type = PTR_TO_STACK; /* we don't have dedicated reg type */ + if (is_kfunc_rcu_protected(meta)) { + if (in_rcu_cs(env)) + st->type |= MEM_RCU; + else + st->type |= PTR_UNTRUSTED; + } st->live |= REG_LIVE_WRITTEN; st->ref_obj_id = i == 0 ? id : 0; st->iter.btf = btf; @@ -1268,7 +1279,7 @@ static bool is_iter_reg_valid_uninit(struct bpf_verifier_env *env, return true; } -static bool is_iter_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg, +static int is_iter_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg, struct btf *btf, u32 btf_id, int nr_slots) { struct bpf_func_state *state = func(env, reg); @@ -1276,26 +1287,28 @@ static bool is_iter_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_ spi = iter_get_spi(env, reg, nr_slots); if (spi < 0) - return false; + return -EINVAL; for (i = 0; i < nr_slots; i++) { struct bpf_stack_state *slot = &state->stack[spi - i]; struct bpf_reg_state *st = &slot->spilled_ptr; + if (st->type & PTR_UNTRUSTED) + return -EPROTO; /* only main (first) slot has ref_obj_id set */ if (i == 0 && !st->ref_obj_id) - return false; + return -EINVAL; if (i != 0 && st->ref_obj_id) - return false; + return -EINVAL; if (st->iter.btf != btf || st->iter.btf_id != btf_id) - return false; + return -EINVAL; for (j = 0; j < BPF_REG_SIZE; j++) if (slot->slot_type[j] != STACK_ITER) - return false; + return -EINVAL; } - return true; + return 0; } /* Check if given stack slot is "special": @@ -7618,15 +7631,24 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id return err; } - err = mark_stack_slots_iter(env, reg, insn_idx, meta->btf, btf_id, nr_slots); + err = mark_stack_slots_iter(env, meta, reg, insn_idx, meta->btf, btf_id, nr_slots); if (err) return err; } else { /* iter_next() or iter_destroy() expect initialized iter state*/ - if (!is_iter_reg_valid_init(env, reg, meta->btf, btf_id, nr_slots)) { + err = is_iter_reg_valid_init(env, reg, meta->btf, btf_id, nr_slots); + switch (err) { + case 0: + break; + case -EINVAL: verbose(env, "expected an initialized iter_%s as arg #%d\n", iter_type_str(meta->btf, btf_id), regno); - return -EINVAL; + return err; + case -EPROTO: + verbose(env, "expected an RCU CS when using %s\n", meta->func_name); + return err; + default: + return err; } spi = iter_get_spi(env, reg, nr_slots); @@ -10209,6 +10231,11 @@ static bool is_kfunc_rcu(struct bpf_kfunc_call_arg_meta *meta) return meta->kfunc_flags & KF_RCU; } +static bool is_kfunc_rcu_protected(struct bpf_kfunc_call_arg_meta *meta) +{ + return meta->kfunc_flags & KF_RCU_PROTECTED; +} + static bool __kfunc_param_match_suffix(const struct btf *btf, const struct btf_param *arg, const char *suffix) @@ -11560,6 +11587,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (env->cur_state->active_rcu_lock) { struct bpf_func_state *state; struct bpf_reg_state *reg; + u32 clear_mask = (1 << STACK_SPILL) | (1 << STACK_ITER); if (in_rbtree_lock_required_cb(env) && (rcu_lock || rcu_unlock)) { verbose(env, "Calling bpf_rcu_read_{lock,unlock} in unnecessary rbtree callback\n"); @@ -11570,7 +11598,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, verbose(env, "nested rcu read lock (kernel function %s)\n", func_name); return -EINVAL; } else if (rcu_unlock) { - bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({ + bpf_for_each_reg_in_vstate_mask(env->cur_state, state, reg, clear_mask, ({ if (reg->type & MEM_RCU) { reg->type &= ~(MEM_RCU | PTR_MAYBE_NULL); reg->type |= PTR_UNTRUSTED;