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selftests/bpf: Add test for key-less BTF hash map

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Create a hash and an rhash map with btf_key_type_id == 0 and expect
bpf_map_create() to fail with -EINVAL; a positive control with a real
key type confirms the rejection is about the key-less BTF and not some
unrelated failure.

Such a map used to be accepted and then NULL-deref in btf_type_show()
when dumped through bpffs.

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://lore.kernel.org/r/20260901104924.346187-5-jiayuan.chen@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Jiayuan Chen 2026-09-01 18:47:38 +08:00 committed by Alexei Starovoitov
parent 5403a383f5
commit 6265b44f2c
1 changed files with 59 additions and 0 deletions
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59
tools/testing/selftests/bpf/prog_tests/btf_map_keyless.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
#include <bpf/btf.h>
/*
* A hash map with a key-less BTF (btf_key_type_id == 0) used to be accepted
* and then NULL-deref in btf_type_show() when dumped through bpffs. A fixed
* kernel rejects it at creation; verify that rejection, with a keyed positive
* control so the -EINVAL is about the missing key type and not some unrelated
* failure.
*/
static void check_keyless(int map_type, __u32 map_flags, int btf_fd, int val_id)
{
LIBBPF_OPTS(bpf_map_create_opts, opts);
int map_fd;
opts.map_flags = map_flags;
opts.btf_fd = btf_fd;
opts.btf_value_type_id = val_id;
/* Positive control: the same map with a real key type is accepted. */
opts.btf_key_type_id = val_id;
map_fd = bpf_map_create(map_type, "keyed_map", 4, 4, 8, &opts);
if (!ASSERT_GE(map_fd, 0, "keyed create is accepted"))
return;
close(map_fd);
/* A key-less BTF must be rejected. */
opts.btf_key_type_id = 0;
map_fd = bpf_map_create(map_type, "keyless_map", 4, 4, 8, &opts);
ASSERT_EQ(map_fd, -EINVAL, "key-less create is rejected");
if (map_fd >= 0)
close(map_fd);
}
void test_btf_map_keyless(void)
{
int btf_fd, val_id;
struct btf *btf;
btf = btf__new_empty();
if (!ASSERT_OK_PTR(btf, "btf__new_empty"))
return;
val_id = btf__add_int(btf, "int", 4, BTF_INT_SIGNED);
if (!ASSERT_GT(val_id, 0, "btf__add_int"))
goto out;
if (!ASSERT_OK(btf__load_into_kernel(btf), "btf__load_into_kernel"))
goto out;
btf_fd = btf__fd(btf);
if (test__start_subtest("hash"))
check_keyless(BPF_MAP_TYPE_HASH, 0, btf_fd, val_id);
if (test__start_subtest("rhash"))
check_keyless(BPF_MAP_TYPE_RHASH, BPF_F_NO_PREALLOC, btf_fd, val_id);
out:
btf__free(btf);
}