From: Kaitao Cheng <[email protected]> If a user holds ownership of a node in the middle of a list, they can directly remove it from the list without strictly adhering to deletion rules from the head or tail.
When a kfunc has only one bpf_list_node parameter, supplement the initialization of the corresponding btf_field. Add a new lock_rec member to struct bpf_reference_state for lock holding detection. This is typically paired with bpf_refcount. After calling bpf_list_del, it is generally necessary to drop the reference to the list node twice to prevent reference count leaks. Signed-off-by: Kaitao Cheng <[email protected]> --- include/linux/bpf_verifier.h | 4 +++ kernel/bpf/btf.c | 33 +++++++++++++++++++--- kernel/bpf/helpers.c | 17 ++++++++++++ kernel/bpf/verifier.c | 54 ++++++++++++++++++++++++++++++++++-- 4 files changed, 101 insertions(+), 7 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index ef8e45a362d9..e1358b62d6cc 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -261,6 +261,10 @@ struct bpf_reference_state { * it matches on unlock. */ void *ptr; + /* For REF_TYPE_LOCK_*: btf_record of the locked object, used for lock + * checking in kfuncs such as bpf_list_del. + */ + struct btf_record *lock_rec; }; struct bpf_retval_range { diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 4872d2a6c42d..8a977c793d56 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3785,7 +3785,6 @@ static int btf_find_field_one(const struct btf *btf, case BPF_RES_SPIN_LOCK: case BPF_TIMER: case BPF_WORKQUEUE: - case BPF_LIST_NODE: case BPF_RB_NODE: case BPF_REFCOUNT: case BPF_TASK_WORK: @@ -3794,6 +3793,27 @@ static int btf_find_field_one(const struct btf *btf, if (ret < 0) return ret; break; + case BPF_LIST_NODE: + ret = btf_find_struct(btf, var_type, off, sz, field_type, + info_cnt ? &info[0] : &tmp); + if (ret < 0) + return ret; + /* graph_root for verifier: container type and node member name */ + if (info_cnt && var_idx >= 0 && (u32)var_idx < btf_type_vlen(var)) { + u32 id; + const struct btf_member *member; + + for (id = 1; id < btf_nr_types(btf); id++) { + if (btf_type_by_id(btf, id) == var) { + info[0].graph_root.value_btf_id = id; + member = btf_type_member(var) + var_idx; + info[0].graph_root.node_name = + __btf_name_by_offset(btf, member->name_off); + break; + } + } + } + break; case BPF_KPTR_UNREF: case BPF_KPTR_REF: case BPF_KPTR_PERCPU: @@ -4138,6 +4158,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type if (ret < 0) goto end; break; + case BPF_LIST_NODE: case BPF_LIST_HEAD: ret = btf_parse_list_head(btf, &rec->fields[i], &info_arr[i]); if (ret < 0) @@ -4148,7 +4169,6 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type if (ret < 0) goto end; break; - case BPF_LIST_NODE: case BPF_RB_NODE: break; default: @@ -4192,20 +4212,25 @@ int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec) int i; /* There are three types that signify ownership of some other type: - * kptr_ref, bpf_list_head, bpf_rb_root. + * kptr_ref, bpf_list_head/node, bpf_rb_root. * kptr_ref only supports storing kernel types, which can't store * references to program allocated local types. * * Hence we only need to ensure that bpf_{list_head,rb_root} ownership * does not form cycles. */ - if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & (BPF_GRAPH_ROOT | BPF_UPTR))) + if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & + (BPF_GRAPH_ROOT | BPF_GRAPH_NODE | BPF_UPTR))) return 0; + for (i = 0; i < rec->cnt; i++) { struct btf_struct_meta *meta; const struct btf_type *t; u32 btf_id; + if (rec->fields[i].type & BPF_GRAPH_NODE) + rec->fields[i].graph_root.value_rec = rec; + if (rec->fields[i].type == BPF_UPTR) { /* The uptr only supports pinning one page and cannot * point to a kernel struct diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 6eb6c82ed2ee..577af62a9f7a 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2459,6 +2459,22 @@ __bpf_kfunc struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) return __bpf_list_del(head, true); } +__bpf_kfunc struct bpf_list_node *bpf_list_del(struct bpf_list_node *node) +{ + struct bpf_list_node_kern *knode = (struct bpf_list_node_kern *)node; + + if (unlikely(!knode)) + return NULL; + + if (WARN_ON_ONCE(!READ_ONCE(knode->owner))) + return NULL; + + list_del_init(&knode->list_head); + WRITE_ONCE(knode->owner, NULL); + + return node; +} + __bpf_kfunc struct bpf_list_node *bpf_list_front(struct bpf_list_head *head) { struct list_head *h = (struct list_head *)head; @@ -4545,6 +4561,7 @@ BTF_ID_FLAGS(func, bpf_list_push_front_impl) BTF_ID_FLAGS(func, bpf_list_push_back_impl) BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL) 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_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a3390190c26e..8a782772dd36 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1536,7 +1536,7 @@ static int acquire_reference(struct bpf_verifier_env *env, int insn_idx) } static int acquire_lock_state(struct bpf_verifier_env *env, int insn_idx, enum ref_state_type type, - int id, void *ptr) + int id, void *ptr, struct btf_record *lock_rec) { struct bpf_verifier_state *state = env->cur_state; struct bpf_reference_state *s; @@ -1547,6 +1547,7 @@ static int acquire_lock_state(struct bpf_verifier_env *env, int insn_idx, enum r s->type = type; s->id = id; s->ptr = ptr; + s->lock_rec = lock_rec; state->active_locks++; state->active_lock_id = id; @@ -1662,6 +1663,23 @@ static struct bpf_reference_state *find_lock_state(struct bpf_verifier_state *st return NULL; } +static bool rec_has_list_matching_node_type(struct bpf_verifier_env *env, + const struct btf_record *rec, + const struct btf *node_btf, u32 node_btf_id) +{ + u32 i; + + for (i = 0; i < rec->cnt; i++) { + if (!(rec->fields[i].type & BPF_LIST_HEAD)) + continue; + if (btf_struct_ids_match(&env->log, node_btf, node_btf_id, 0, + rec->fields[i].graph_root.btf, + rec->fields[i].graph_root.value_btf_id, true)) + return true; + } + return false; +} + static void update_peak_states(struct bpf_verifier_env *env) { u32 cur_states; @@ -8576,7 +8594,8 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno, int flags) type = REF_TYPE_RES_LOCK; else type = REF_TYPE_LOCK; - err = acquire_lock_state(env, env->insn_idx, type, reg->id, ptr); + err = acquire_lock_state(env, env->insn_idx, type, reg->id, ptr, + reg_btf_record(reg)); if (err < 0) { verbose(env, "Failed to acquire lock state\n"); return err; @@ -12431,6 +12450,7 @@ enum special_kfunc_type { KF_bpf_list_push_back_impl, KF_bpf_list_pop_front, KF_bpf_list_pop_back, + KF_bpf_list_del, KF_bpf_list_front, KF_bpf_list_back, KF_bpf_cast_to_kern_ctx, @@ -12491,6 +12511,7 @@ BTF_ID(func, bpf_list_push_front_impl) BTF_ID(func, bpf_list_push_back_impl) BTF_ID(func, bpf_list_pop_front) 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_cast_to_kern_ctx) @@ -12966,6 +12987,7 @@ static bool is_bpf_list_api_kfunc(u32 btf_id) btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] || btf_id == special_kfunc_list[KF_bpf_list_pop_front] || btf_id == special_kfunc_list[KF_bpf_list_pop_back] || + btf_id == special_kfunc_list[KF_bpf_list_del] || btf_id == special_kfunc_list[KF_bpf_list_front] || btf_id == special_kfunc_list[KF_bpf_list_back]; } @@ -13088,7 +13110,8 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env, switch (node_field_type) { case BPF_LIST_NODE: ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] || - kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_back_impl]); + kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] || + kfunc_btf_id == special_kfunc_list[KF_bpf_list_del]); break; case BPF_RB_NODE: ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] || @@ -13211,6 +13234,9 @@ __process_kf_arg_ptr_to_graph_node(struct bpf_verifier_env *env, return -EINVAL; } + if (!*node_field) + *node_field = field; + field = *node_field; et = btf_type_by_id(field->graph_root.btf, field->graph_root.value_btf_id); @@ -13237,6 +13263,28 @@ __process_kf_arg_ptr_to_graph_node(struct bpf_verifier_env *env, return -EINVAL; } + /* 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. + */ + if (node_field_type == BPF_LIST_NODE && + meta->func_id == special_kfunc_list[KF_bpf_list_del]) { + struct bpf_verifier_state *cur = env->cur_state; + + for (int i = 0; i < cur->acquired_refs; i++) { + struct bpf_reference_state *s = &cur->refs[i]; + + if (!(s->type & REF_TYPE_LOCK_MASK) || !s->lock_rec) + continue; + + if (rec_has_list_matching_node_type(env, s->lock_rec, + reg->btf, reg->btf_id)) + return 0; + } + verbose(env, "bpf_spin_lock must be held for bpf_list_del\n"); + return -EINVAL; + } + return 0; } -- 2.50.1 (Apple Git-155)
