Commit fb301594 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add a failure test for bpf_kptr_xchg() with local kptr 



For a bpf_kptr_xchg() with local kptr, if the map value kptr type and
allocated local obj type does not match, with the previous patch,
the below verifier error message will be logged:
  R2 is of type <allocated local obj type> but <map value kptr type> is expected

Without the previous patch, the test will have unexpected success.

Signed-off-by: default avatarYonghong Song <yonghong.song@linux.dev>
Acked-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230822050058.2887354-1-yonghong.song@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ab6c637a

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

+9 −1
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
#include <network_helpers.h>



#include "local_kptr_stash.skel.h"

#include "local_kptr_stash_fail.skel.h"

static void test_local_kptr_stash_simple(void)

{

	LIBBPF_OPTS(bpf_test_run_opts, opts,
@@ -51,10 +52,17 @@ static void test_local_kptr_stash_unstash(void) 
	local_kptr_stash__destroy(skel);

}



void test_local_kptr_stash_success(void)

static void test_local_kptr_stash_fail(void)

{

	RUN_TESTS(local_kptr_stash_fail);

}



void test_local_kptr_stash(void)

{

	if (test__start_subtest("local_kptr_stash_simple"))

		test_local_kptr_stash_simple();

	if (test__start_subtest("local_kptr_stash_unstash"))

		test_local_kptr_stash_unstash();

	if (test__start_subtest("local_kptr_stash_fail"))

		test_local_kptr_stash_fail();

}

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

0 → 100644
+65 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */



#include <vmlinux.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_core_read.h>

#include "../bpf_experimental.h"

#include "bpf_misc.h"



struct node_data {

	long key;

	long data;

	struct bpf_rb_node node;

};



struct map_value {

	struct node_data __kptr *node;

};



struct node_data2 {

	long key[4];

};



/* This is necessary so that LLVM generates BTF for node_data struct

 * If it's not included, a fwd reference for node_data will be generated but

 * no struct. Example BTF of "node" field in map_value when not included:

 *

 * [10] PTR '(anon)' type_id=35

 * [34] FWD 'node_data' fwd_kind=struct

 * [35] TYPE_TAG 'kptr_ref' type_id=34

 */

struct node_data *just_here_because_btf_bug;



struct {

	__uint(type, BPF_MAP_TYPE_ARRAY);

	__type(key, int);

	__type(value, struct map_value);

	__uint(max_entries, 2);

} some_nodes SEC(".maps");



SEC("tc")

__failure __msg("invalid kptr access, R2 type=ptr_node_data2 expected=ptr_node_data")

long stash_rb_nodes(void *ctx)

{

	struct map_value *mapval;

	struct node_data2 *res;

	int idx = 0;



	mapval = bpf_map_lookup_elem(&some_nodes, &idx);

	if (!mapval)

		return 1;



	res = bpf_obj_new(typeof(*res));

	if (!res)

		return 1;

	res->key[0] = 40;



	res = bpf_kptr_xchg(&mapval->node, res);

	if (res)

		bpf_obj_drop(res);

	return 0;

}



char _license[] SEC("license") = "GPL";