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/drivers/clk/spear/clk.c b/drivers/clk/spear/clk.c
new file mode 100644
index 000000000..50847cccd
--- /dev/null
+++ b/drivers/clk/spear/clk.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2012 ST Microelectronics
+ * Viresh Kumar <vireshk@kernel.org>
+ *
+ * SPEAr clk - Common routines
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/types.h>
+#include "clk.h"
+
+long clk_round_rate_index(struct clk_hw *hw, unsigned long drate,
+		unsigned long parent_rate, clk_calc_rate calc_rate, u8 rtbl_cnt,
+		int *index)
+{
+	unsigned long prev_rate, rate = 0;
+
+	for (*index = 0; *index < rtbl_cnt; (*index)++) {
+		prev_rate = rate;
+		rate = calc_rate(hw, parent_rate, *index);
+		if (drate < rate) {
+			/* previous clock was best */
+			if (*index) {
+				rate = prev_rate;
+				(*index)--;
+			}
+			break;
+		}
+	}
+
+	if ((*index) == rtbl_cnt)
+		(*index)--;
+
+	return rate;
+}