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: 120933984460 ("bpf: Implement mprog API on top of existing cgroup progs") Cc: Maciej Żenczykowski Cc: Lorenzo Colitti Signed-off-by: Yuyang Huang --- .../selftests/bpf/prog_tests/bpf_attr_size.c | 69 +++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_attr_size.c diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_attr_size.c b/tools/testing/selftests/bpf/prog_tests/bpf_attr_size.c new file mode 100644 index 000000000000..32159dc64da8 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/bpf_attr_size.c @@ -0,0 +1,69 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Google LLC */ +#include +#include +#include +#include +#include +#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(); +} -- 2.54.0.823.g6e5bcc1fc9-goog