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, 63 insertions, 0 deletions

diff --git a/include/kunit/try-catch.h b/include/kunit/try-catch.h
new file mode 100644
index 000000000..d4e1a5b98
--- /dev/null
+++ b/include/kunit/try-catch.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * An API to allow a function, that may fail, to be executed, and recover in a
+ * controlled manner.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_TRY_CATCH_H
+#define _KUNIT_TRY_CATCH_H
+
+#include <linux/types.h>
+
+typedef void (*kunit_try_catch_func_t)(void *);
+
+struct kunit;
+
+/**
+ * struct kunit_try_catch - provides a generic way to run code which might fail.
+ * @test: The test case that is currently being executed.
+ * @try_result: Contains any errno obtained while running test case.
+ * @try: The function, the test case, to attempt to run.
+ * @catch: The function called if @try bails out.
+ * @context: used to pass user data to the try and catch functions.
+ *
+ * kunit_try_catch provides a generic, architecture independent way to execute
+ * an arbitrary function of type kunit_try_catch_func_t which may bail out by
+ * calling kunit_try_catch_throw(). If kunit_try_catch_throw() is called, @try
+ * is stopped at the site of invocation and @catch is called.
+ *
+ * struct kunit_try_catch provides a generic interface for the functionality
+ * needed to implement kunit->abort() which in turn is needed for implementing
+ * assertions. Assertions allow stating a precondition for a test simplifying
+ * how test cases are written and presented.
+ *
+ * Assertions are like expectations, except they abort (call
+ * kunit_try_catch_throw()) when the specified condition is not met. This is
+ * useful when you look at a test case as a logical statement about some piece
+ * of code, where assertions are the premises for the test case, and the
+ * conclusion is a set of predicates, rather expectations, that must all be
+ * true. If your premises are violated, it does not makes sense to continue.
+ */
+struct kunit_try_catch {
+	/* private: internal use only. */
+	struct kunit *test;
+	int try_result;
+	kunit_try_catch_func_t try;
+	kunit_try_catch_func_t catch;
+	unsigned long timeout;
+	void *context;
+};
+
+void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context);
+
+void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch);
+
+static inline int kunit_try_catch_get_result(struct kunit_try_catch *try_catch)
+{
+	return try_catch->try_result;
+}
+
+#endif /* _KUNIT_TRY_CATCH_H */