selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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 <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 139 insertions, 0 deletions

diff --git a/tools/perf/tests/openat-syscall-all-cpus.c b/tools/perf/tests/openat-syscall-all-cpus.c
new file mode 100644
index 000000000..0be43f8db
--- /dev/null
+++ b/tools/perf/tests/openat-syscall-all-cpus.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <inttypes.h>
+/* For the CPU_* macros */
+#include <sched.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <api/fs/fs.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <api/fs/tracing_path.h>
+#include "evsel.h"
+#include "tests.h"
+#include "thread_map.h"
+#include <perf/cpumap.h>
+#include "debug.h"
+#include "stat.h"
+#include "util/counts.h"
+
+static int test__openat_syscall_event_on_all_cpus(struct test_suite *test __maybe_unused,
+						  int subtest __maybe_unused)
+{
+	int err = TEST_FAIL, fd;
+	unsigned int idx;
+	struct perf_cpu cpu;
+	struct perf_cpu_map *cpus;
+	struct evsel *evsel;
+	unsigned int nr_openat_calls = 111, i;
+	cpu_set_t cpu_set;
+	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 -1;
+	}
+
+	cpus = perf_cpu_map__new_online_cpus();
+	if (cpus == NULL) {
+		pr_debug("perf_cpu_map__new\n");
+		goto out_thread_map_delete;
+	}
+
+	CPU_ZERO(&cpu_set);
+
+	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_cpu_map_delete;
+	}
+
+	if (evsel__open(evsel, cpus, 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;
+	}
+
+	perf_cpu_map__for_each_cpu(cpu, idx, cpus) {
+		unsigned int ncalls = nr_openat_calls + idx;
+		/*
+		 * XXX eventually lift this restriction in a way that
+		 * keeps perf building on older glibc installations
+		 * without CPU_ALLOC. 1024 cpus in 2010 still seems
+		 * a reasonable upper limit tho :-)
+		 */
+		if (cpu.cpu >= CPU_SETSIZE) {
+			pr_debug("Ignoring CPU %d\n", cpu.cpu);
+			continue;
+		}
+
+		CPU_SET(cpu.cpu, &cpu_set);
+		if (sched_setaffinity(0, sizeof(cpu_set), &cpu_set) < 0) {
+			pr_debug("sched_setaffinity() failed on CPU %d: %s ",
+				 cpu.cpu,
+				 str_error_r(errno, sbuf, sizeof(sbuf)));
+			goto out_close_fd;
+		}
+		for (i = 0; i < ncalls; ++i) {
+			fd = openat(0, "/etc/passwd", O_RDONLY);
+			close(fd);
+		}
+		CPU_CLR(cpu.cpu, &cpu_set);
+	}
+
+	evsel->core.cpus = perf_cpu_map__get(cpus);
+
+	err = TEST_OK;
+
+	perf_cpu_map__for_each_cpu(cpu, idx, cpus) {
+		unsigned int expected;
+
+		if (cpu.cpu >= CPU_SETSIZE)
+			continue;
+
+		if (evsel__read_on_cpu(evsel, idx, 0) < 0) {
+			pr_debug("evsel__read_on_cpu\n");
+			err = TEST_FAIL;
+			break;
+		}
+
+		expected = nr_openat_calls + idx;
+		if (perf_counts(evsel->counts, idx, 0)->val != expected) {
+			pr_debug("evsel__read_on_cpu: expected to intercept %d calls on cpu %d, got %" PRIu64 "\n",
+				 expected, cpu.cpu, perf_counts(evsel->counts, idx, 0)->val);
+			err = TEST_FAIL;
+		}
+	}
+
+	evsel__free_counts(evsel);
+out_close_fd:
+	perf_evsel__close_fd(&evsel->core);
+out_evsel_delete:
+	evsel__delete(evsel);
+out_cpu_map_delete:
+	perf_cpu_map__put(cpus);
+out_thread_map_delete:
+	perf_thread_map__put(threads);
+	return err;
+}
+
+
+static struct test_case tests__openat_syscall_event_on_all_cpus[] = {
+	TEST_CASE_REASON("Detect openat syscall event on all cpus",
+			 openat_syscall_event_on_all_cpus,
+			 "permissions"),
+	{	.name = NULL, }
+};
+
+struct test_suite suite__openat_syscall_event_on_all_cpus = {
+	.desc = "Detect openat syscall event on all cpus",
+	.test_cases = tests__openat_syscall_event_on_all_cpus,
+};