diff options
| -rw-r--r-- | kernel/bpf/btf.c | 134 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/linked_list.c | 4 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/local_kptr_ownership.c | 296 |
3 files changed, 384 insertions, 50 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index d67a169ba2bb..d870bc5e50bc 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -4268,13 +4268,10 @@ 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 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. + /* + * Check fields which require the complete BTF and initialize runtime + * metadata. Ownership relationships are validated after every record has + * been fixed up. */ if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & (BPF_GRAPH_ROOT | BPF_UPTR))) return 0; @@ -4305,51 +4302,88 @@ int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec) if (!meta) return -EFAULT; rec->fields[i].graph_root.value_rec = meta->record; + } + return 0; +} - /* We need to set value_rec for all root types, but no need - * to check ownership cycle for a type unless it's also a - * node type. - */ - if (!(rec->field_mask & BPF_GRAPH_NODE)) +static int btf_owned_type_idx(const struct btf *btf, struct btf_struct_metas *tab, + const struct btf_field *field) +{ + struct btf_struct_meta *meta; + u32 btf_id; + + if (field->type & BPF_GRAPH_ROOT) { + btf_id = field->graph_root.value_btf_id; + } else if (field->type == BPF_KPTR_REF || field->type == BPF_KPTR_PERCPU) { + if (btf_is_kernel(field->kptr.btf)) + return -ENOENT; + btf_id = field->kptr.btf_id; + } else { + return -ENOENT; + } + + meta = btf_find_struct_meta(btf, btf_id); + if (!meta) + return field->type & BPF_GRAPH_ROOT ? -EFAULT : -ENOENT; + return meta - tab->types; +} + +/* + * Each ownership edge adds kernel frames through bpf_obj_free_fields() and + * __bpf_obj_drop_impl(). Keep the bound deliberately small because object + * destruction can itself run below a BPF call chain. A final pointee without + * special fields is not present in the struct metadata table and adds only a + * non-recursing drop. + */ +#define BTF_MAX_OWNERSHIP_DEPTH 8 + +static int btf_ownership_depth(const struct btf *btf, + struct btf_struct_metas *tab, u8 *depth, + int idx, int depth_left) +{ + const struct btf_record *rec = tab->types[idx].record; + int i, ret, max_depth = 0; + + if (!depth_left) + return -ELOOP; + if (depth[idx]) + goto done; + + for (i = 0; i < rec->cnt; i++) { + ret = btf_owned_type_idx(btf, tab, &rec->fields[i]); + if (ret == -ENOENT) continue; + if (ret < 0) + return ret; + ret = btf_ownership_depth(btf, tab, depth, ret, depth_left - 1); + if (ret < 0) + return ret; + max_depth = max(max_depth, ret); + } + depth[idx] = max_depth + 1; +done: + return depth[idx] > depth_left ? -ELOOP : depth[idx]; +} - /* We need to ensure ownership acyclicity among all types. The - * proper way to do it would be to topologically sort all BTF - * IDs based on the ownership edges, since there can be multiple - * bpf_{list_head,rb_node} in a type. Instead, we use the - * following resaoning: - * - * - A type can only be owned by another type in user BTF if it - * has a bpf_{list,rb}_node. Let's call these node types. - * - A type can only _own_ another type in user BTF if it has a - * bpf_{list_head,rb_root}. Let's call these root types. - * - * We ensure that if a type is both a root and node, its - * element types cannot be root types. - * - * To ensure acyclicity: - * - * When A is an root type but not a node, its ownership - * chain can be: - * A -> B -> C - * Where: - * - A is an root, e.g. has bpf_rb_root. - * - B is both a root and node, e.g. has bpf_rb_node and - * bpf_list_head. - * - C is only an root, e.g. has bpf_list_node - * - * When A is both a root and node, some other type already - * owns it in the BTF domain, hence it can not own - * another root type through any of the ownership edges. - * A -> B - * Where: - * - A is both an root and node. - * - B is only an node. - */ - if (meta->record->field_mask & BPF_GRAPH_ROOT) - return -ELOOP; +static int btf_check_ownership_depth(const struct btf *btf, + struct btf_struct_metas *tab) +{ + u8 *depth; + int i, ret = 0; + + depth = kvcalloc(tab->cnt, sizeof(*depth), GFP_KERNEL | __GFP_NOWARN); + if (!depth) + return -ENOMEM; + + for (i = 0; i < tab->cnt; i++) { + ret = btf_ownership_depth(btf, tab, depth, i, + BTF_MAX_OWNERSHIP_DEPTH); + if (ret < 0) + break; + ret = 0; } - return 0; + kvfree(depth); + return ret; } static void __btf_struct_show(const struct btf *btf, const struct btf_type *t, @@ -6044,6 +6078,10 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, if (err < 0) goto errout_meta; } + + err = btf_check_ownership_depth(btf, struct_meta_tab); + if (err < 0) + goto errout_meta; } err = bpf_log_attr_finalize(attr_log, &env->log); diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c index c3d133c6a00d..52fabbee3dd5 100644 --- a/tools/testing/selftests/bpf/prog_tests/linked_list.c +++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c @@ -714,7 +714,7 @@ static void test_btf(void) break; err = btf__load_into_kernel(btf); - ASSERT_EQ(err, -ELOOP, "check btf"); + ASSERT_EQ(err, 0, "check btf"); btf__free(btf); break; } @@ -773,7 +773,7 @@ static void test_btf(void) break; err = btf__load_into_kernel(btf); - ASSERT_EQ(err, -ELOOP, "check btf"); + ASSERT_EQ(err, 0, "check btf"); btf__free(btf); break; } diff --git a/tools/testing/selftests/bpf/prog_tests/local_kptr_ownership.c b/tools/testing/selftests/bpf/prog_tests/local_kptr_ownership.c new file mode 100644 index 000000000000..a487aa68f2ee --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/local_kptr_ownership.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ + +#include <bpf/btf.h> +#include <linux/btf.h> +#include <test_progs.h> + +#define SPIN_LOCK 2 +#define LIST_HEAD 3 +#define LIST_NODE 4 +/* Keep in sync with BTF_MAX_OWNERSHIP_DEPTH. */ +#define MAX_OWNERSHIP_DEPTH 8 + +static struct btf *init_btf(void) +{ + struct btf *btf; + int id; + + btf = btf__new_empty(); + if (!ASSERT_OK_PTR(btf, "btf__new_empty")) + return NULL; + id = btf__add_int(btf, "int", 4, BTF_INT_SIGNED); + if (!ASSERT_EQ(id, 1, "btf__add_int")) + goto err_out; + id = btf__add_struct(btf, "bpf_spin_lock", 4); + if (!ASSERT_EQ(id, SPIN_LOCK, "btf__add_struct bpf_spin_lock")) + goto err_out; + id = btf__add_struct(btf, "bpf_list_head", 16); + if (!ASSERT_EQ(id, LIST_HEAD, "btf__add_struct bpf_list_head")) + goto err_out; + id = btf__add_struct(btf, "bpf_list_node", 24); + if (!ASSERT_EQ(id, LIST_NODE, "btf__add_struct bpf_list_node")) + goto err_out; + return btf; + +err_out: + btf__free(btf); + return NULL; +} + +static int add_local_kptr(struct btf *btf, int pointee_id, const char *tag) +{ + int id; + + id = btf__add_type_tag(btf, tag, pointee_id); + if (!ASSERT_GT(id, 0, "btf__add_type_tag")) + return id; + id = btf__add_ptr(btf, id); + ASSERT_GT(id, 0, "btf__add_ptr"); + return id; +} + +static void test_self_cycle(const char *tag, int expected_err) +{ + struct btf *btf; + int id, err; + + btf = init_btf(); + if (!ASSERT_OK_PTR(btf, "init_btf")) + return; + id = add_local_kptr(btf, 7, tag); + if (id <= 0) + goto out; + id = btf__add_struct(btf, "self_cycle", 8); + if (!ASSERT_EQ(id, 7, "btf__add_struct self_cycle")) + goto out; + err = btf__add_field(btf, "next", 6, 0, 0); + if (!ASSERT_OK(err, "btf__add_field self_cycle::next")) + goto out; + + err = btf__load_into_kernel(btf); + ASSERT_EQ(err, expected_err, "check btf"); +out: + btf__free(btf); +} + +static void test_aba_cycle(void) +{ + struct btf *btf; + int id, err; + + btf = init_btf(); + if (!ASSERT_OK_PTR(btf, "init_btf")) + return; + id = add_local_kptr(btf, 10, "kptr"); + if (id <= 0) + goto out; + id = add_local_kptr(btf, 9, "kptr"); + if (id <= 0) + goto out; + id = btf__add_struct(btf, "cycle_a", 8); + if (!ASSERT_EQ(id, 9, "btf__add_struct cycle_a")) + goto out; + err = btf__add_field(btf, "b", 6, 0, 0); + if (!ASSERT_OK(err, "btf__add_field cycle_a::b")) + goto out; + id = btf__add_struct(btf, "cycle_b", 8); + if (!ASSERT_EQ(id, 10, "btf__add_struct cycle_b")) + goto out; + err = btf__add_field(btf, "a", 8, 0, 0); + if (!ASSERT_OK(err, "btf__add_field cycle_b::a")) + goto out; + + err = btf__load_into_kernel(btf); + ASSERT_EQ(err, -ELOOP, "check btf"); +out: + btf__free(btf); +} + +static void test_mixed_cycle(void) +{ + struct btf *btf; + int id, err; + + btf = init_btf(); + if (!ASSERT_OK_PTR(btf, "init_btf")) + return; + id = add_local_kptr(btf, 7, "kptr"); + if (id <= 0) + goto out; + id = btf__add_struct(btf, "mixed_owner", 20); + if (!ASSERT_EQ(id, 7, "btf__add_struct mixed_owner")) + goto out; + err = btf__add_field(btf, "root", LIST_HEAD, 0, 0); + if (!ASSERT_OK(err, "btf__add_field mixed_owner::root")) + goto out; + err = btf__add_field(btf, "lock", SPIN_LOCK, 128, 0); + if (!ASSERT_OK(err, "btf__add_field mixed_owner::lock")) + goto out; + id = btf__add_decl_tag(btf, "contains:mixed_node:node", 7, 0); + if (!ASSERT_EQ(id, 8, "btf__add_decl_tag mixed_owner")) + goto out; + id = btf__add_struct(btf, "mixed_node", 32); + if (!ASSERT_EQ(id, 9, "btf__add_struct mixed_node")) + goto out; + err = btf__add_field(btf, "node", LIST_NODE, 0, 0); + if (!ASSERT_OK(err, "btf__add_field mixed_node::node")) + goto out; + err = btf__add_field(btf, "owner", 6, 192, 0); + if (!ASSERT_OK(err, "btf__add_field mixed_node::owner")) + goto out; + + err = btf__load_into_kernel(btf); + ASSERT_EQ(err, -ELOOP, "check btf"); +out: + btf__free(btf); +} + +static void test_acyclic_depth(int depth, bool child_first, bool shared_suffix, int expected_err) +{ + int ptr_id[MAX_OWNERSHIP_DEPTH + 1]; + int first_struct_id; + struct btf *btf; + int id, err, i, n, pointee_id; + + btf = init_btf(); + if (!ASSERT_OK_PTR(btf, "init_btf")) + return; + first_struct_id = 5 + 2 * depth; + for (i = 0; i < depth; i++) { + if (i == depth - 1) + pointee_id = first_struct_id + depth; + else + pointee_id = first_struct_id + (child_first ? depth - 2 - i : i + 1); + ptr_id[i] = add_local_kptr(btf, pointee_id, "kptr"); + if (ptr_id[i] <= 0) + goto out; + } + for (n = 0; n < depth; n++) { + char name[32]; + int offset = 0; + + i = child_first ? depth - 1 - n : n; + snprintf(name, sizeof(name), "owner_%d", i); + id = btf__add_struct(btf, name, shared_suffix && !i ? 16 : 8); + if (!ASSERT_EQ(id, first_struct_id + n, "btf__add_struct owner")) + goto out; + if (shared_suffix && !i) { + /* + * Visit the shared suffix through the shorter path before + * reaching it again with less remaining depth. + */ + err = btf__add_field(btf, "suffix", ptr_id[1], 0, 0); + if (!ASSERT_OK(err, "btf__add_field owner::suffix")) + goto out; + offset = 64; + } + err = btf__add_field(btf, "next", ptr_id[i], offset, 0); + if (!ASSERT_OK(err, "btf__add_field owner::next")) + goto out; + } + id = btf__add_struct(btf, "plain_leaf", 4); + if (!ASSERT_EQ(id, first_struct_id + depth, "btf__add_struct plain_leaf")) + goto out; + + err = btf__load_into_kernel(btf); + ASSERT_EQ(err, expected_err, "check btf"); +out: + btf__free(btf); +} + +static void test_graph_depth(bool rbtree, int depth, int expected_err) +{ + int root_type = LIST_HEAD, node_type = LIST_NODE, node_size = 24; + int id, err, i, lock_off, root_off, size; + struct btf *btf; + + btf = init_btf(); + if (!ASSERT_OK_PTR(btf, "init_btf")) + return; + if (rbtree) { + root_type = btf__add_struct(btf, "bpf_rb_root", 16); + if (!ASSERT_GT(root_type, 0, "btf__add_struct bpf_rb_root")) + goto out; + node_type = btf__add_struct(btf, "bpf_rb_node", 32); + if (!ASSERT_GT(node_type, 0, "btf__add_struct bpf_rb_node")) + goto out; + node_size = 32; + } + + for (i = 0; i < depth; i++) { + char name[32], tag[64]; + + lock_off = i ? node_size : 0; + root_off = lock_off + 8; + size = i == depth - 1 ? node_size : root_off + 16; + snprintf(name, sizeof(name), "graph_owner_%d", i); + id = btf__add_struct(btf, name, size); + if (!ASSERT_GT(id, 0, "btf__add_struct graph_owner")) + goto out; + if (i) { + err = btf__add_field(btf, "node", node_type, 0, 0); + if (!ASSERT_OK(err, "btf__add_field graph_owner::node")) + goto out; + } + if (i == depth - 1) + continue; + err = btf__add_field(btf, "lock", SPIN_LOCK, lock_off * 8, 0); + if (!ASSERT_OK(err, "btf__add_field graph_owner::lock")) + goto out; + err = btf__add_field(btf, "root", root_type, root_off * 8, 0); + if (!ASSERT_OK(err, "btf__add_field graph_owner::root")) + goto out; + snprintf(tag, sizeof(tag), "contains:graph_owner_%d:node", i + 1); + err = btf__add_decl_tag(btf, tag, id, i ? 2 : 1); + if (!ASSERT_GT(err, 0, "btf__add_decl_tag graph_owner")) + goto out; + } + + err = btf__load_into_kernel(btf); + ASSERT_EQ(err, expected_err, "check btf"); +out: + btf__free(btf); +} + +void test_local_kptr_ownership(void) +{ + if (test__start_subtest("self_cycle")) + test_self_cycle("kptr", -ELOOP); + if (test__start_subtest("untrusted_self_cycle")) + test_self_cycle("kptr_untrusted", 0); + if (test__start_subtest("percpu_self_cycle")) + test_self_cycle("percpu_kptr", -ELOOP); + if (test__start_subtest("ABA_cycle")) + test_aba_cycle(); + if (test__start_subtest("mixed_graph_root_cycle")) + test_mixed_cycle(); + if (test__start_subtest("max_acyclic")) + test_acyclic_depth(MAX_OWNERSHIP_DEPTH, false, false, 0); + if (test__start_subtest("too_deep_acyclic")) + test_acyclic_depth(MAX_OWNERSHIP_DEPTH + 1, false, false, -ELOOP); + if (test__start_subtest("max_acyclic_child_first")) + test_acyclic_depth(MAX_OWNERSHIP_DEPTH, true, false, 0); + if (test__start_subtest("too_deep_acyclic_child_first")) + test_acyclic_depth(MAX_OWNERSHIP_DEPTH + 1, true, false, -ELOOP); + if (test__start_subtest("max_acyclic_shared_suffix")) + test_acyclic_depth(MAX_OWNERSHIP_DEPTH, false, true, 0); + if (test__start_subtest("too_deep_acyclic_shared_suffix")) + test_acyclic_depth(MAX_OWNERSHIP_DEPTH + 1, false, true, -ELOOP); + if (test__start_subtest("list_three_types")) + test_graph_depth(false, 3, 0); + if (test__start_subtest("list_four_types")) + test_graph_depth(false, 4, 0); + if (test__start_subtest("list_max_depth")) + test_graph_depth(false, MAX_OWNERSHIP_DEPTH, 0); + if (test__start_subtest("list_too_deep")) + test_graph_depth(false, MAX_OWNERSHIP_DEPTH + 1, -ELOOP); + if (test__start_subtest("rbtree_three_types")) + test_graph_depth(true, 3, 0); + if (test__start_subtest("rbtree_four_types")) + test_graph_depth(true, 4, 0); + if (test__start_subtest("rbtree_max_depth")) + test_graph_depth(true, MAX_OWNERSHIP_DEPTH, 0); + if (test__start_subtest("rbtree_too_deep")) + test_graph_depth(true, MAX_OWNERSHIP_DEPTH + 1, -ELOOP); +} |