From: Kaitao Cheng <[email protected]> Add a new kfunc bpf_list_add_impl(head, new, prev, meta, off) that inserts 'new' 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.
We have added an additional parameter bpf_list_head *head to bpf_list_add_impl, as the verifier requires the head parameter to check whether the lock is being held. Returns 0 on success, -EINVAL if 'prev' is not in a list or 'new' is already in a list (or duplicate insertion). On failure, the kernel drops the passed-in node. Signed-off-by: Kaitao Cheng <[email protected]> --- kernel/bpf/helpers.c | 56 ++++++++++++++++++++++++++++++------------- kernel/bpf/verifier.c | 13 ++++++++-- 2 files changed, 50 insertions(+), 19 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 01b74c4ac00d..407520fde668 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2379,11 +2379,12 @@ __bpf_kfunc void *bpf_refcount_acquire_impl(void *p__refcounted_kptr, void *meta return (void *)p__refcounted_kptr; } -static int __bpf_list_add(struct bpf_list_node_kern *node, - struct bpf_list_head *head, - bool tail, struct btf_record *rec, u64 off) +static int __bpf_list_add(struct bpf_list_head *head, + struct bpf_list_node_kern *new, + struct list_head *prev, + struct btf_record *rec, u64 off) { - struct list_head *n = &node->list_head, *h = (void *)head; + struct list_head *n = &new->list_head, *h = (void *)head; /* If list_head was 0-initialized by map, bpf_obj_init_field wasn't * called on its fields, so init here @@ -2391,39 +2392,59 @@ static int __bpf_list_add(struct bpf_list_node_kern *node, if (unlikely(!h->next)) INIT_LIST_HEAD(h); - /* node->owner != NULL implies !list_empty(n), no need to separately + /* When prev is not the list head, it must be a node in this list. */ + if (prev != h && WARN_ON_ONCE(READ_ONCE(container_of( + prev, struct bpf_list_node_kern, list_head)->owner) != head)) + goto fail; + + /* new->owner != NULL implies !list_empty(n), no need to separately * check the latter */ - if (cmpxchg(&node->owner, NULL, BPF_PTR_POISON)) { - /* Only called from BPF prog, no need to migrate_disable */ - __bpf_obj_drop_impl((void *)n - off, rec, false); - return -EINVAL; - } - - tail ? list_add_tail(n, h) : list_add(n, h); - WRITE_ONCE(node->owner, head); + if (cmpxchg(&new->owner, NULL, BPF_PTR_POISON)) + goto fail; + list_add(n, prev); + WRITE_ONCE(new->owner, head); return 0; + +fail: + /* Only called from BPF prog, no need to migrate_disable */ + __bpf_obj_drop_impl((void *)n - off, rec, false); + return -EINVAL; } __bpf_kfunc int bpf_list_push_front_impl(struct bpf_list_head *head, struct bpf_list_node *node, void *meta__ign, u64 off) { - struct bpf_list_node_kern *n = (void *)node; + struct bpf_list_node_kern *new = (void *)node; struct btf_struct_meta *meta = meta__ign; + struct list_head *h = (void *)head; - return __bpf_list_add(n, head, false, meta ? meta->record : NULL, off); + return __bpf_list_add(head, new, h, meta ? meta->record : NULL, off); } __bpf_kfunc int bpf_list_push_back_impl(struct bpf_list_head *head, struct bpf_list_node *node, void *meta__ign, u64 off) { - struct bpf_list_node_kern *n = (void *)node; + struct bpf_list_node_kern *new = (void *)node; + struct btf_struct_meta *meta = meta__ign; + struct list_head *h = (void *)head; + + return __bpf_list_add(head, new, h->prev, meta ? meta->record : NULL, off); +} + +__bpf_kfunc int bpf_list_add_impl(struct bpf_list_head *head, + struct bpf_list_node *new, + struct bpf_list_node *prev, + void *meta__ign, u64 off) +{ + struct bpf_list_node_kern *kn = (void *)new, *kp = (void *)prev; struct btf_struct_meta *meta = meta__ign; - return __bpf_list_add(n, head, true, meta ? meta->record : NULL, off); + return __bpf_list_add(head, kn, &kp->list_head, + meta ? meta->record : NULL, off); } static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, @@ -4563,6 +4584,7 @@ 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 c9557d3fb8dd..5f55b68ed935 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12459,6 +12459,7 @@ enum special_kfunc_type { KF_bpf_refcount_acquire_impl, KF_bpf_list_push_front_impl, KF_bpf_list_push_back_impl, + KF_bpf_list_add_impl, KF_bpf_list_pop_front, KF_bpf_list_pop_back, KF_bpf_list_del, @@ -12520,6 +12521,7 @@ BTF_ID(func, bpf_obj_drop_impl) BTF_ID(func, bpf_refcount_acquire_impl) BTF_ID(func, bpf_list_push_front_impl) BTF_ID(func, bpf_list_push_back_impl) +BTF_ID(func, bpf_list_add_impl) BTF_ID(func, bpf_list_pop_front) BTF_ID(func, bpf_list_pop_back) BTF_ID(func, bpf_list_del) @@ -12996,6 +12998,7 @@ static bool is_bpf_list_api_kfunc(u32 btf_id) { return btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] || btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] || + btf_id == special_kfunc_list[KF_bpf_list_add_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] || @@ -13122,6 +13125,7 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env, 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_add_impl] || kfunc_btf_id == special_kfunc_list[KF_bpf_list_del]); break; case BPF_RB_NODE: @@ -14264,6 +14268,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (meta.func_id == special_kfunc_list[KF_bpf_list_push_front_impl] || meta.func_id == special_kfunc_list[KF_bpf_list_push_back_impl] || + meta.func_id == special_kfunc_list[KF_bpf_list_add_impl] || meta.func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { release_ref_obj_id = regs[BPF_REG_2].ref_obj_id; insn_aux->insert_off = regs[BPF_REG_2].off; @@ -23230,13 +23235,17 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, *cnt = 3; } else if (desc->func_id == special_kfunc_list[KF_bpf_list_push_back_impl] || desc->func_id == special_kfunc_list[KF_bpf_list_push_front_impl] || + desc->func_id == special_kfunc_list[KF_bpf_list_add_impl] || desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta; int struct_meta_reg = BPF_REG_3; int node_offset_reg = BPF_REG_4; - /* rbtree_add has extra 'less' arg, so args-to-fixup are in diff regs */ - if (desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { + /* list/rbtree_add_impl have an extra arg (prev/less), + * so args-to-fixup are in different regs. + */ + if (desc->func_id == special_kfunc_list[KF_bpf_list_add_impl] || + desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { struct_meta_reg = BPF_REG_4; node_offset_reg = BPF_REG_5; } -- 2.50.1 (Apple Git-155)
