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selftests/bpf: add verification for BPF_PROG_QUERY attr size boundaries

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Add a new selftest to verify that the BPF syscall (specifically
BPF_PROG_QUERY) correctly handles different user-declared attribute sizes.

Specifically, verify that:
- For cgroup queries, a query with a size that covers 'prog_cnt' but is
  smaller than 'revision' (OLD_QUERY_SIZE) succeeds, but does not write
  to 'revision' (verifying backward compatibility).
- A query with full size (FULL_QUERY_SIZE) succeeds and writes both
  'prog_cnt' and 'revision'.

Fixes: 1209339844 ("bpf: Implement mprog API on top of existing cgroup progs")
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Yuyang Huang <yuyanghuang@google.com>
Link: https://lore.kernel.org/r/20260531075600.4058207-3-yuyanghuang@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yuyang Huang 2026-05-31 15:56:00 +08:00 committed by Alexei Starovoitov
parent 21c4b99b27
commit 5add3a4ad1
1 changed files with 69 additions and 0 deletions
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69
tools/testing/selftests/bpf/prog_tests/bpf_attr_size.c Normal file
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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2026 Google LLC */
#include <linux/bpf.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <test_progs.h>
#include <cgroup_helpers.h>
#include "cgroup_skb_direct_packet_access.skel.h"
#define OLD_QUERY_SIZE offsetofend(union bpf_attr, query.prog_cnt)
#define FULL_QUERY_SIZE offsetofend(union bpf_attr, query.revision)
static void test_query_size_boundaries(void)
{
struct cgroup_skb_direct_packet_access *skel;
struct bpf_link *link = NULL;
union bpf_attr attr;
int cg_fd = -1;
int err;
skel = cgroup_skb_direct_packet_access__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_load"))
return;
cg_fd = test__join_cgroup("/attr_size_cg");
if (!ASSERT_GE(cg_fd, 0, "join_cgroup"))
goto cleanup;
link = bpf_program__attach_cgroup(skel->progs.direct_packet_access,
cg_fd);
if (!ASSERT_OK_PTR(link, "cg_attach"))
goto cleanup;
memset(&attr, 0, sizeof(attr));
attr.query.target_fd = cg_fd;
attr.query.attach_type = BPF_CGROUP_INET_INGRESS;
attr.query.revision = 0xdeadbeefdeadbeefULL;
err = syscall(__NR_bpf, BPF_PROG_QUERY, &attr, OLD_QUERY_SIZE);
if (ASSERT_OK(err, "query_old_size")) {
ASSERT_EQ(attr.query.prog_cnt, 1, "prog_cnt_written_old");
ASSERT_EQ(attr.query.revision, 0xdeadbeefdeadbeefULL,
"revision_not_written_old");
}
memset(&attr, 0, sizeof(attr));
attr.query.target_fd = cg_fd;
attr.query.attach_type = BPF_CGROUP_INET_INGRESS;
err = syscall(__NR_bpf, BPF_PROG_QUERY, &attr, FULL_QUERY_SIZE);
if (!ASSERT_OK(err, "query_full_size"))
goto cleanup;
ASSERT_EQ(attr.query.prog_cnt, 1, "prog_cnt_written");
ASSERT_GT(attr.query.revision, 0, "revision_written");
cleanup:
if (link)
bpf_link__destroy(link);
if (cg_fd >= 0)
close(cg_fd);
cgroup_skb_direct_packet_access__destroy(skel);
}
void test_bpf_attr_size(void)
{
if (test__start_subtest("query_size_boundaries"))
test_query_size_boundaries();
}