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, 48 insertions, 0 deletions

diff --git a/tools/perf/util/pmu.l b/tools/perf/util/pmu.l
new file mode 100644
index 000000000..67b247be6
--- /dev/null
+++ b/tools/perf/util/pmu.l
@@ -0,0 +1,48 @@
+%option prefix="perf_pmu_"
+%option reentrant
+%option bison-bridge
+
+%{
+#include <stdlib.h>
+#include <linux/bitops.h>
+#include "pmu.h"
+#include "pmu-bison.h"
+
+char *perf_pmu_get_text(yyscan_t yyscanner);
+YYSTYPE *perf_pmu_get_lval(yyscan_t yyscanner);
+
+static int value(yyscan_t scanner, int base)
+{
+	YYSTYPE *yylval = perf_pmu_get_lval(scanner);
+	char *text = perf_pmu_get_text(scanner);
+	long num;
+
+	errno = 0;
+	num = strtoul(text, NULL, base);
+	if (errno)
+		return PP_ERROR;
+
+	yylval->num = num;
+	return PP_VALUE;
+}
+
+%}
+
+num_dec         [0-9]+
+
+%%
+
+{num_dec}	{ return value(yyscanner, 10); }
+config		{ return PP_CONFIG; }
+-		{ return '-'; }
+:		{ return ':'; }
+,		{ return ','; }
+.		{ ; }
+\n		{ ; }
+
+%%
+
+int perf_pmu_wrap(void *scanner __maybe_unused)
+{
+	return 1;
+}