selftests/bpf: Add refcounted_kptr tests

Test refcounted local kptr functionality added in previous patches in
the series.

Usecases which pass verification:

* Add refcounted local kptr to both tree and list. Then, read and -
  possibly, depending on test variant - delete from tree, then list.
  * Also test doing read-and-maybe-delete in opposite order
* Stash a refcounted local kptr in a map_value, then add it to a
  rbtree. Read from both, possibly deleting after tree read.
* Add refcounted local kptr to both tree and list. Then, try reading and
  deleting twice from one of the collections.
* bpf_refcount_acquire of just-added non-owning ref should work, as
  should bpf_refcount_acquire of owning ref just out of bpf_obj_new

Usecases which fail verification:

* The simple successful bpf_refcount_acquire cases from above should
  both fail to verify if the newly-acquired owning ref is not dropped
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230415201811.343116-10-davemarchevsky@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "refcounted_kptr.skel.h"
+#include "refcounted_kptr_fail.skel.h"
+
+void test_refcounted_kptr(void)
+{
+	RUN_TESTS(refcounted_kptr);
+}
+
+void test_refcounted_kptr_fail(void)
+{
+	RUN_TESTS(refcounted_kptr_fail);
+}

tools/testing/selftests/bpf/progs/refcounted_kptr.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_misc.h"
+#include "bpf_experimental.h"
+
+struct node_data {
+	long key;
+	long list_data;
+	struct bpf_rb_node r;
+	struct bpf_list_node l;
+	struct bpf_refcount ref;
+};
+
+struct map_value {
+	struct node_data __kptr *node;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} stashed_nodes SEC(".maps");
+
+struct node_acquire {
+	long key;
+	long data;
+	struct bpf_rb_node node;
+	struct bpf_refcount refcount;
+};
+
+#define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8)))
+private(A) struct bpf_spin_lock lock;
+private(A) struct bpf_rb_root root __contains(node_data, r);
+private(A) struct bpf_list_head head __contains(node_data, l);
+
+private(B) struct bpf_spin_lock alock;
+private(B) struct bpf_rb_root aroot __contains(node_acquire, node);
+
+static bool less(struct bpf_rb_node *node_a, const struct bpf_rb_node *node_b)
+{
+	struct node_data *a;
+	struct node_data *b;
+
+	a = container_of(node_a, struct node_data, r);
+	b = container_of(node_b, struct node_data, r);
+
+	return a->key < b->key;
+}
+
+static bool less_a(struct bpf_rb_node *a, const struct bpf_rb_node *b)
+{
+	struct node_acquire *node_a;
+	struct node_acquire *node_b;
+
+	node_a = container_of(a, struct node_acquire, node);
+	node_b = container_of(b, struct node_acquire, node);
+
+	return node_a->key < node_b->key;
+}
+
+static long __insert_in_tree_and_list(struct bpf_list_head *head,
+				      struct bpf_rb_root *root,
+				      struct bpf_spin_lock *lock)
+{
+	struct node_data *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return -1;
+
+	m = bpf_refcount_acquire(n);
+	m->key = 123;
+	m->list_data = 456;
+
+	bpf_spin_lock(lock);
+	if (bpf_rbtree_add(root, &n->r, less)) {
+		/* Failure to insert - unexpected */
+		bpf_spin_unlock(lock);
+		bpf_obj_drop(m);
+		return -2;
+	}
+	bpf_spin_unlock(lock);
+
+	bpf_spin_lock(lock);
+	if (bpf_list_push_front(head, &m->l)) {
+		/* Failure to insert - unexpected */
+		bpf_spin_unlock(lock);
+		return -3;
+	}
+	bpf_spin_unlock(lock);
+	return 0;
+}
+
+static long __stash_map_insert_tree(int idx, int val, struct bpf_rb_root *root,
+				    struct bpf_spin_lock *lock)
+{
+	struct map_value *mapval;
+	struct node_data *n, *m;
+
+	mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
+	if (!mapval)
+		return -1;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return -2;
+
+	n->key = val;
+	m = bpf_refcount_acquire(n);
+
+	n = bpf_kptr_xchg(&mapval->node, n);
+	if (n) {
+		bpf_obj_drop(n);
+		bpf_obj_drop(m);
+		return -3;
+	}
+
+	bpf_spin_lock(lock);
+	if (bpf_rbtree_add(root, &m->r, less)) {
+		/* Failure to insert - unexpected */
+		bpf_spin_unlock(lock);
+		return -4;
+	}
+	bpf_spin_unlock(lock);
+	return 0;
+}
+
+static long __read_from_tree(struct bpf_rb_root *root,
+			     struct bpf_spin_lock *lock,
+			     bool remove_from_tree)
+{
+	struct bpf_rb_node *rb;
+	struct node_data *n;
+	long res = -99;
+
+	bpf_spin_lock(lock);
+
+	rb = bpf_rbtree_first(root);
+	if (!rb) {
+		bpf_spin_unlock(lock);
+		return -1;
+	}
+
+	n = container_of(rb, struct node_data, r);
+	res = n->key;
+
+	if (!remove_from_tree) {
+		bpf_spin_unlock(lock);
+		return res;
+	}
+
+	rb = bpf_rbtree_remove(root, rb);
+	bpf_spin_unlock(lock);
+	if (!rb)
+		return -2;
+	n = container_of(rb, struct node_data, r);
+	bpf_obj_drop(n);
+	return res;
+}
+
+static long __read_from_list(struct bpf_list_head *head,
+			     struct bpf_spin_lock *lock,
+			     bool remove_from_list)
+{
+	struct bpf_list_node *l;
+	struct node_data *n;
+	long res = -99;
+
+	bpf_spin_lock(lock);
+
+	l = bpf_list_pop_front(head);
+	if (!l) {
+		bpf_spin_unlock(lock);
+		return -1;
+	}
+
+	n = container_of(l, struct node_data, l);
+	res = n->list_data;
+
+	if (!remove_from_list) {
+		if (bpf_list_push_back(head, &n->l)) {
+			bpf_spin_unlock(lock);
+			return -2;
+		}
+	}
+
+	bpf_spin_unlock(lock);
+
+	if (remove_from_list)
+		bpf_obj_drop(n);
+	return res;
+}
+
+static long __read_from_unstash(int idx)
+{
+	struct node_data *n = NULL;
+	struct map_value *mapval;
+	long val = -99;
+
+	mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
+	if (!mapval)
+		return -1;
+
+	n = bpf_kptr_xchg(&mapval->node, n);
+	if (!n)
+		return -2;
+
+	val = n->key;
+	bpf_obj_drop(n);
+	return val;
+}
+
+#define INSERT_READ_BOTH(rem_tree, rem_list, desc)			\
+SEC("tc")								\
+__description(desc)							\
+__success __retval(579)							\
+long insert_and_remove_tree_##rem_tree##_list_##rem_list(void *ctx)	\
+{									\
+	long err, tree_data, list_data;					\
+									\
+	err = __insert_in_tree_and_list(&head, &root, &lock);		\
+	if (err)							\
+		return err;						\
+									\
+	err = __read_from_tree(&root, &lock, rem_tree);			\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		tree_data = err;					\
+									\
+	err = __read_from_list(&head, &lock, rem_list);			\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		list_data = err;					\
+									\
+	return tree_data + list_data;					\
+}
+
+/* After successful insert of struct node_data into both collections:
+ *   - it should have refcount = 2
+ *   - removing / not removing the node_data from a collection after
+ *     reading should have no effect on ability to read / remove from
+ *     the other collection
+ */
+INSERT_READ_BOTH(true, true, "insert_read_both: remove from tree + list");
+INSERT_READ_BOTH(false, false, "insert_read_both: remove from neither");
+INSERT_READ_BOTH(true, false, "insert_read_both: remove from tree");
+INSERT_READ_BOTH(false, true, "insert_read_both: remove from list");
+
+#undef INSERT_READ_BOTH
+#define INSERT_READ_BOTH(rem_tree, rem_list, desc)			\
+SEC("tc")								\
+__description(desc)							\
+__success __retval(579)							\
+long insert_and_remove_lf_tree_##rem_tree##_list_##rem_list(void *ctx)	\
+{									\
+	long err, tree_data, list_data;					\
+									\
+	err = __insert_in_tree_and_list(&head, &root, &lock);		\
+	if (err)							\
+		return err;						\
+									\
+	err = __read_from_list(&head, &lock, rem_list);			\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		list_data = err;					\
+									\
+	err = __read_from_tree(&root, &lock, rem_tree);			\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		tree_data = err;					\
+									\
+	return tree_data + list_data;					\
+}
+
+/* Similar to insert_read_both, but list data is read and possibly removed
+ * first
+ *
+ * Results should be no different than reading and possibly removing rbtree
+ * node first
+ */
+INSERT_READ_BOTH(true, true, "insert_read_both_list_first: remove from tree + list");
+INSERT_READ_BOTH(false, false, "insert_read_both_list_first: remove from neither");
+INSERT_READ_BOTH(true, false, "insert_read_both_list_first: remove from tree");
+INSERT_READ_BOTH(false, true, "insert_read_both_list_first: remove from list");
+
+#define INSERT_DOUBLE_READ_AND_DEL(read_fn, read_root, desc)		\
+SEC("tc")								\
+__description(desc)							\
+__success __retval(-1)							\
+long insert_double_##read_fn##_and_del_##read_root(void *ctx)		\
+{									\
+	long err, list_data;						\
+									\
+	err = __insert_in_tree_and_list(&head, &root, &lock);		\
+	if (err)							\
+		return err;						\
+									\
+	err = read_fn(&read_root, &lock, true);				\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		list_data = err;					\
+									\
+	err = read_fn(&read_root, &lock, true);				\
+	if (err < 0)							\
+		return err;						\
+									\
+	return err + list_data;						\
+}
+
+/* Insert into both tree and list, then try reading-and-removing from either twice
+ *
+ * The second read-and-remove should fail on read step since the node has
+ * already been removed
+ */
+INSERT_DOUBLE_READ_AND_DEL(__read_from_tree, root, "insert_double_del: 2x read-and-del from tree");
+INSERT_DOUBLE_READ_AND_DEL(__read_from_list, head, "insert_double_del: 2x read-and-del from list");
+
+#define INSERT_STASH_READ(rem_tree, desc)				\
+SEC("tc")								\
+__description(desc)							\
+__success __retval(84)							\
+long insert_rbtree_and_stash__del_tree_##rem_tree(void *ctx)		\
+{									\
+	long err, tree_data, map_data;					\
+									\
+	err = __stash_map_insert_tree(0, 42, &root, &lock);		\
+	if (err)							\
+		return err;						\
+									\
+	err = __read_from_tree(&root, &lock, rem_tree);			\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		tree_data = err;					\
+									\
+	err = __read_from_unstash(0);					\
+	if (err < 0)							\
+		return err;						\
+	else								\
+		map_data = err;						\
+									\
+	return tree_data + map_data;					\
+}
+
+/* Stash a refcounted node in map_val, insert same node into tree, then try
+ * reading data from tree then unstashed map_val, possibly removing from tree
+ *
+ * Removing from tree should have no effect on map_val kptr validity
+ */
+INSERT_STASH_READ(true, "insert_stash_read: remove from tree");
+INSERT_STASH_READ(false, "insert_stash_read: don't remove from tree");
+
+SEC("tc")
+__success
+long rbtree_refcounted_node_ref_escapes(void *ctx)
+{
+	struct node_acquire *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return 1;
+
+	bpf_spin_lock(&alock);
+	bpf_rbtree_add(&aroot, &n->node, less_a);
+	m = bpf_refcount_acquire(n);
+	bpf_spin_unlock(&alock);
+
+	m->key = 2;
+	bpf_obj_drop(m);
+	return 0;
+}
+
+SEC("tc")
+__success
+long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)
+{
+	struct node_acquire *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return 1;
+
+	m = bpf_refcount_acquire(n);
+	m->key = 2;
+
+	bpf_spin_lock(&alock);
+	bpf_rbtree_add(&aroot, &n->node, less_a);
+	bpf_spin_unlock(&alock);
+
+	bpf_obj_drop(m);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c

+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_experimental.h"
+#include "bpf_misc.h"
+
+struct node_acquire {
+	long key;
+	long data;
+	struct bpf_rb_node node;
+	struct bpf_refcount refcount;
+};
+
+#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+private(A) struct bpf_spin_lock glock;
+private(A) struct bpf_rb_root groot __contains(node_acquire, node);
+
+static bool less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
+{
+	struct node_acquire *node_a;
+	struct node_acquire *node_b;
+
+	node_a = container_of(a, struct node_acquire, node);
+	node_b = container_of(b, struct node_acquire, node);
+
+	return node_a->key < node_b->key;
+}
+
+SEC("?tc")
+__failure __msg("Unreleased reference id=3 alloc_insn=21")
+long rbtree_refcounted_node_ref_escapes(void *ctx)
+{
+	struct node_acquire *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return 1;
+
+	bpf_spin_lock(&glock);
+	bpf_rbtree_add(&groot, &n->node, less);
+	/* m becomes an owning ref but is never drop'd or added to a tree */
+	m = bpf_refcount_acquire(n);
+	bpf_spin_unlock(&glock);
+
+	m->key = 2;
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("Unreleased reference id=3 alloc_insn=9")
+long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)
+{
+	struct node_acquire *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return 1;
+
+	/* m becomes an owning ref but is never drop'd or added to a tree */
+	m = bpf_refcount_acquire(n);
+	m->key = 2;
+
+	bpf_spin_lock(&glock);
+	bpf_rbtree_add(&groot, &n->node, less);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";