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, 36 insertions, 0 deletions

diff --git a/tools/include/nolibc/assert.h b/tools/include/nolibc/assert.h
new file mode 100644
index 000000000..84ff8ad9a
--- /dev/null
+++ b/tools/include/nolibc/assert.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Assert for NOLIBC
+ * Copyright (C) 2026 Thomas Weißschuh <linux@weissschuh.net>
+ */
+
+/* make sure to include all global symbols */
+#include "nolibc.h"
+
+#ifndef _NOLIBC_ASSERT_H
+#define _NOLIBC_ASSERT_H
+
+#include "errno.h"
+#include "stdio.h"
+#include "stdlib.h"
+
+#endif /* _NOLIBC_ASSERT_H */
+
+/* NDEBUG needs to be evaluated on *each* inclusion */
+#ifdef assert
+#undef assert
+#endif
+
+#ifndef NDEBUG
+#define assert(expr)									\
+({											\
+	if (!(expr)) {									\
+		fprintf(stderr, "%s: %s:%d: %s: Assertion `%s' failed.\n",		\
+			program_invocation_short_name, __FILE__, __LINE__, __func__,	\
+			#expr);								\
+		abort();								\
+	}										\
+})
+#else
+#define assert(expr) ((void)0)
+#endif