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Mon, 02 Mar 2026 04:41:03 -0800 (PST) From: Chengkaitao To: martin.lau@linux.dev, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, linux-kselftest@vger.kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 3/6] bpf: add bpf_list_add_impl to insert node after a given list node Date: Mon, 2 Mar 2026 20:40:25 +0800 Message-ID: <20260302124028.82420-4-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260302124028.82420-1-pilgrimtao@gmail.com> References: <20260302124028.82420-1-pilgrimtao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Kaitao Cheng Add a new kfunc bpf_list_add_impl(prev, node, meta, off) that inserts 'node' after 'prev' in the BPF linked list. Both must be in the same list; 'prev' must already be in the list. The new node must be an owning reference (e.g. from bpf_obj_new); the kfunc consumes that reference and the node becomes non-owning once inserted. Returns 0 on success, -EINVAL if prev is not in a list or node is already in a list (or duplicate insertion). On failure, the kernel drops the passed-in node. Signed-off-by: Kaitao Cheng --- kernel/bpf/helpers.c | 34 ++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 23 ++++++++++++++++------- 2 files changed, 50 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 577af62a9f7a..d212962d4ed6 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2495,6 +2495,39 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(stru= ct bpf_list_head *head) return (struct bpf_list_node *)h->prev; } =20 +static int __bpf_list_add_after(struct bpf_list_node_kern *prev, + struct bpf_list_node_kern *node, + struct btf_record *rec, u64 off) +{ + struct bpf_list_head *head; + struct list_head *n =3D &node->list_head, *p =3D &prev->list_head; + + head =3D READ_ONCE(prev->owner); + if (unlikely(!head)) + goto fail; + + if (cmpxchg(&node->owner, NULL, BPF_PTR_POISON)) + goto fail; + + list_add(n, p); + WRITE_ONCE(node->owner, head); + return 0; + +fail: + __bpf_obj_drop_impl((void *)n - off, rec, false); + return -EINVAL; +} + +__bpf_kfunc int bpf_list_add_impl(struct bpf_list_node *prev, + struct bpf_list_node *node, + void *meta__ign, u64 off) +{ + struct bpf_list_node_kern *n =3D (void *)node, *p =3D (void *)prev; + struct btf_struct_meta *meta =3D meta__ign; + + return __bpf_list_add_after(p, n, meta ? meta->record : NULL, off); +} + __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, struct bpf_rb_node *node) { @@ -4564,6 +4597,7 @@ BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF= _RET_NULL) BTF_ID_FLAGS(func, bpf_list_del, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL) BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_list_add_impl) BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE) BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_RET_NULL) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8a782772dd36..f5ee11779a5c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12453,6 +12453,7 @@ enum special_kfunc_type { KF_bpf_list_del, KF_bpf_list_front, KF_bpf_list_back, + KF_bpf_list_add_impl, KF_bpf_cast_to_kern_ctx, KF_bpf_rdonly_cast, KF_bpf_rcu_read_lock, @@ -12514,6 +12515,7 @@ BTF_ID(func, bpf_list_pop_back) BTF_ID(func, bpf_list_del) BTF_ID(func, bpf_list_front) BTF_ID(func, bpf_list_back) +BTF_ID(func, bpf_list_add_impl) BTF_ID(func, bpf_cast_to_kern_ctx) BTF_ID(func, bpf_rdonly_cast) BTF_ID(func, bpf_rcu_read_lock) @@ -12989,7 +12991,8 @@ static bool is_bpf_list_api_kfunc(u32 btf_id) btf_id =3D=3D special_kfunc_list[KF_bpf_list_pop_back] || btf_id =3D=3D special_kfunc_list[KF_bpf_list_del] || btf_id =3D=3D special_kfunc_list[KF_bpf_list_front] || - btf_id =3D=3D special_kfunc_list[KF_bpf_list_back]; + btf_id =3D=3D special_kfunc_list[KF_bpf_list_back] || + btf_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl]; } =20 static bool is_bpf_rbtree_api_kfunc(u32 btf_id) @@ -13111,7 +13114,8 @@ static bool check_kfunc_is_graph_node_api(struct bp= f_verifier_env *env, case BPF_LIST_NODE: ret =3D (kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_push_front_i= mpl] || kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_push_back_impl= ] || - kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_del]); + kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_del] || + kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl]); break; case BPF_RB_NODE: ret =3D (kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_rbtree_remove] || @@ -13263,12 +13267,15 @@ __process_kf_arg_ptr_to_graph_node(struct bpf_ver= ifier_env *env, return -EINVAL; } =20 - /* bpf_list_del: require list head's lock. Use refs[] REF_TYPE_LOCK_MASK - * only. At lock time we stored the locked object's btf_record in ref-> - * lock_rec, so we can get the list value type from the ref directly. + /* When there is no bpf_list_head in the parameter list, to prevent BPF + * programs from calling bpf_list APIs without holding the spinlock, + * we need to acquire the list head's lock. At lock time we stored the + * locked object's btf_record in ref->lock_rec, so we can get the list + * value type from the ref directly. */ if (node_field_type =3D=3D BPF_LIST_NODE && - meta->func_id =3D=3D special_kfunc_list[KF_bpf_list_del]) { + (meta->func_id =3D=3D special_kfunc_list[KF_bpf_list_del] || + meta->func_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl])) { struct bpf_verifier_state *cur =3D env->cur_state; =20 for (int i =3D 0; i < cur->acquired_refs; i++) { @@ -13281,7 +13288,7 @@ __process_kf_arg_ptr_to_graph_node(struct bpf_verif= ier_env *env, reg->btf, reg->btf_id)) return 0; } - verbose(env, "bpf_spin_lock must be held for bpf_list_del\n"); + verbose(env, "bpf_spin_lock must be held for bpf_list api\n"); return -EINVAL; } =20 @@ -14278,6 +14285,7 @@ static int check_kfunc_call(struct bpf_verifier_env= *env, struct bpf_insn *insn, =20 if (meta.func_id =3D=3D special_kfunc_list[KF_bpf_list_push_front_impl] || meta.func_id =3D=3D special_kfunc_list[KF_bpf_list_push_back_impl] || + meta.func_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl] || meta.func_id =3D=3D special_kfunc_list[KF_bpf_rbtree_add_impl]) { release_ref_obj_id =3D regs[BPF_REG_2].ref_obj_id; insn_aux->insert_off =3D regs[BPF_REG_2].off; @@ -23244,6 +23252,7 @@ static int fixup_kfunc_call(struct bpf_verifier_env= *env, struct bpf_insn *insn, *cnt =3D 3; } else if (desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_push_back_= impl] || desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_push_front_impl] = || + desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl] || desc->func_id =3D=3D special_kfunc_list[KF_bpf_rbtree_add_impl]) { struct btf_struct_meta *kptr_struct_meta =3D env->insn_aux_data[insn_idx= ].kptr_struct_meta; int struct_meta_reg =3D BPF_REG_3; --=20 2.50.1 (Apple Git-155)