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, 41 insertions, 0 deletions

diff --git a/drivers/hwmon/lm75.h b/drivers/hwmon/lm75.h
new file mode 100644
index 000000000..b803ada5e
--- /dev/null
+++ b/drivers/hwmon/lm75.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * lm75.h - Part of lm_sensors, Linux kernel modules for hardware monitoring
+ * Copyright (c) 2003 Mark M. Hoffman <mhoffman@lightlink.com>
+ */
+
+/*
+ * This file contains common code for encoding/decoding LM75 type
+ * temperature readings, which are emulated by many of the chips
+ * we support.  As the user is unlikely to load more than one driver
+ * which contains this code, we don't worry about the wasted space.
+ */
+
+#include <linux/minmax.h>
+#include <linux/types.h>
+
+/* straight from the datasheet */
+#define LM75_TEMP_MIN (-55000)
+#define LM75_TEMP_MAX 125000
+#define LM75_SHUTDOWN 0x01
+
+/*
+ * TEMP: 0.001C/bit (-55C to +125C)
+ * REG: (0.5C/bit, two's complement) << 7
+ */
+static inline u16 LM75_TEMP_TO_REG(long temp)
+{
+	int ntemp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
+
+	ntemp += (ntemp < 0 ? -250 : 250);
+	return (u16)((ntemp / 500) << 7);
+}
+
+static inline int LM75_TEMP_FROM_REG(u16 reg)
+{
+	/*
+	 * use integer division instead of equivalent right shift to
+	 * guarantee arithmetic shift and preserve the sign
+	 */
+	return ((s16)reg / 128) * 500;
+}