From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- tools/perf/tests/openat-syscall.c | 84 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 tools/perf/tests/openat-syscall.c (limited to 'tools/perf/tests/openat-syscall.c') diff --git a/tools/perf/tests/openat-syscall.c b/tools/perf/tests/openat-syscall.c new file mode 100644 index 000000000..b54cbe5f1 --- /dev/null +++ b/tools/perf/tests/openat-syscall.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include "thread_map.h" +#include "evsel.h" +#include "debug.h" +#include "tests.h" +#include "util/counts.h" + +static int test__openat_syscall_event(struct test_suite *test __maybe_unused, + int subtest __maybe_unused) +{ + int err = TEST_FAIL, fd; + struct evsel *evsel; + unsigned int nr_openat_calls = 111, i; + struct perf_thread_map *threads = thread_map__new_by_tid(getpid()); + char sbuf[STRERR_BUFSIZE]; + char errbuf[BUFSIZ]; + + if (threads == NULL) { + pr_debug("thread_map__new\n"); + return TEST_FAIL; + } + + evsel = evsel__newtp("syscalls", "sys_enter_openat"); + if (IS_ERR(evsel)) { + tracing_path__strerror_open_tp(errno, errbuf, sizeof(errbuf), "syscalls", "sys_enter_openat"); + pr_debug("%s\n", errbuf); + err = TEST_SKIP; + goto out_thread_map_delete; + } + + if (evsel__open_per_thread(evsel, threads) < 0) { + pr_debug("failed to open counter: %s, " + "tweak /proc/sys/kernel/perf_event_paranoid?\n", + str_error_r(errno, sbuf, sizeof(sbuf))); + err = TEST_SKIP; + goto out_evsel_delete; + } + + for (i = 0; i < nr_openat_calls; ++i) { + fd = openat(0, "/etc/passwd", O_RDONLY); + close(fd); + } + + if (evsel__read_on_cpu(evsel, 0, 0) < 0) { + pr_debug("evsel__read_on_cpu\n"); + goto out_close_fd; + } + + if (perf_counts(evsel->counts, 0, 0)->val != nr_openat_calls) { + pr_debug("evsel__read_on_cpu: expected to intercept %d calls, got %" PRIu64 "\n", + nr_openat_calls, perf_counts(evsel->counts, 0, 0)->val); + goto out_close_fd; + } + + err = TEST_OK; +out_close_fd: + perf_evsel__close_fd(&evsel->core); +out_evsel_delete: + evsel__delete(evsel); +out_thread_map_delete: + perf_thread_map__put(threads); + return err; +} + +static struct test_case tests__openat_syscall_event[] = { + TEST_CASE_REASON("Detect openat syscall event", + openat_syscall_event, + "permissions"), + { .name = NULL, } +}; + +struct test_suite suite__openat_syscall_event = { + .desc = "Detect openat syscall event", + .test_cases = tests__openat_syscall_event, +}; -- cgit v1.3.1