From: Martin KaFai Lau Date: Tue, 6 May 2025 01:58:51 +0000 (-0700) Subject: bpf: Allow refcounted bpf_rb_node used in bpf_rbtree_{remove,left,right} X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=2ddef1783c43ba81a05dec0a5781ebbc61a3c089;p=linux-2.6-microblaze.git bpf: Allow refcounted bpf_rb_node used in bpf_rbtree_{remove,left,right} The bpf_rbtree_{remove,left,right} requires the root's lock to be held. They also check the node_internal->owner is still owned by that root before proceeding, so it is safe to allow refcounted bpf_rb_node pointer to be used in these kfuncs. In a bpf fq implementation which is much closer to the kernel fq, https://lore.kernel.org/bpf/20250418224652.105998-13-martin.lau@linux.dev/, a networking flow (allocated by bpf_obj_new) can be added to two different rbtrees. There are cases that the flow is searched from one rbtree, held the refcount of the flow, and then removed from another rbtree: struct fq_flow { struct bpf_rb_node fq_node; struct bpf_rb_node rate_node; struct bpf_refcount refcount; unsigned long sk_long; }; int bpf_fq_enqueue(...) { /* ... */ bpf_spin_lock(&root->lock); while (can_loop) { /* ... */ if (!p) break; gc_f = bpf_rb_entry(p, struct fq_flow, fq_node); if (gc_f->sk_long == sk_long) { f = bpf_refcount_acquire(gc_f); break; } /* ... */ } bpf_spin_unlock(&root->lock); if (f) { bpf_spin_lock(&q->lock); bpf_rbtree_remove(&q->delayed, &f->rate_node); bpf_spin_unlock(&q->lock); } } bpf_rbtree_{left,right} do not need this change but are relaxed together with bpf_rbtree_remove instead of adding extra verifier logic to exclude these kfuncs. To avoid bi-sect failure, this patch also changes the selftests together. The "rbtree_api_remove_unadded_node" is not expecting verifier's error. The test now expects bpf_rbtree_remove(&groot, &m->node) to return NULL. The test uses __retval(0) to ensure this NULL return value. Some of the "only take non-owning..." failure messages are changed also. Acked-by: Kumar Kartikeya Dwivedi Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20250506015857.817950-5-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 51a17e64a0a9..9093a351b0b3 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -13229,8 +13229,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ return -EINVAL; } } else { - if (!type_is_non_owning_ref(reg->type) || reg->ref_obj_id) { - verbose(env, "%s node input must be non-owning ref\n", func_name); + if (!type_is_non_owning_ref(reg->type) && !reg->ref_obj_id) { + verbose(env, "%s can only take non-owning or refcounted bpf_rb_node pointer\n", func_name); return -EINVAL; } if (in_rbtree_lock_required_cb(env)) { diff --git a/tools/testing/selftests/bpf/progs/rbtree_fail.c b/tools/testing/selftests/bpf/progs/rbtree_fail.c index dbd5eee8e25e..4acb6af2dfe3 100644 --- a/tools/testing/selftests/bpf/progs/rbtree_fail.c +++ b/tools/testing/selftests/bpf/progs/rbtree_fail.c @@ -69,11 +69,11 @@ long rbtree_api_nolock_first(void *ctx) } SEC("?tc") -__failure __msg("rbtree_remove node input must be non-owning ref") +__retval(0) long rbtree_api_remove_unadded_node(void *ctx) { struct node_data *n, *m; - struct bpf_rb_node *res; + struct bpf_rb_node *res_n, *res_m; n = bpf_obj_new(typeof(*n)); if (!n) @@ -88,19 +88,20 @@ long rbtree_api_remove_unadded_node(void *ctx) bpf_spin_lock(&glock); bpf_rbtree_add(&groot, &n->node, less); - /* This remove should pass verifier */ - res = bpf_rbtree_remove(&groot, &n->node); - n = container_of(res, struct node_data, node); + res_n = bpf_rbtree_remove(&groot, &n->node); - /* This remove shouldn't, m isn't in an rbtree */ - res = bpf_rbtree_remove(&groot, &m->node); - m = container_of(res, struct node_data, node); + res_m = bpf_rbtree_remove(&groot, &m->node); bpf_spin_unlock(&glock); - if (n) - bpf_obj_drop(n); - if (m) - bpf_obj_drop(m); + bpf_obj_drop(m); + if (res_n) + bpf_obj_drop(container_of(res_n, struct node_data, node)); + if (res_m) { + bpf_obj_drop(container_of(res_m, struct node_data, node)); + /* m was not added to the rbtree */ + return 2; + } + return 0; } @@ -178,7 +179,7 @@ err_out: } SEC("?tc") -__failure __msg("rbtree_remove node input must be non-owning ref") +__failure __msg("bpf_rbtree_remove can only take non-owning or refcounted bpf_rb_node pointer") long rbtree_api_add_release_unlock_escape(void *ctx) { struct node_data *n; @@ -202,7 +203,7 @@ long rbtree_api_add_release_unlock_escape(void *ctx) } SEC("?tc") -__failure __msg("rbtree_remove node input must be non-owning ref") +__failure __msg("bpf_rbtree_remove can only take non-owning or refcounted bpf_rb_node pointer") long rbtree_api_first_release_unlock_escape(void *ctx) { struct bpf_rb_node *res;