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, 23 insertions, 0 deletions

diff --git a/drivers/clk/mxs/clk.c b/drivers/clk/mxs/clk.c
new file mode 100644
index 000000000..2fe78ba99
--- /dev/null
+++ b/drivers/clk/mxs/clk.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2012 Freescale Semiconductor, Inc.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/jiffies.h>
+#include <linux/spinlock.h>
+#include "clk.h"
+
+DEFINE_SPINLOCK(mxs_lock);
+
+int mxs_clk_wait(void __iomem *reg, u8 shift)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(10);
+
+	while (readl_relaxed(reg) & (1 << shift))
+		if (time_after(jiffies, timeout))
+			return -ETIMEDOUT;
+
+	return 0;
+}