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, 46 insertions, 0 deletions

diff --git a/drivers/md/dm-uevent.h b/drivers/md/dm-uevent.h
new file mode 100644
index 000000000..12a5d4fb7
--- /dev/null
+++ b/drivers/md/dm-uevent.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Device Mapper Uevent Support
+ *
+ * Copyright IBM Corporation, 2007
+ *	Author: Mike Anderson <andmike@linux.vnet.ibm.com>
+ */
+#ifndef DM_UEVENT_H
+#define DM_UEVENT_H
+
+enum dm_uevent_type {
+	DM_UEVENT_PATH_FAILED,
+	DM_UEVENT_PATH_REINSTATED,
+};
+
+#ifdef CONFIG_DM_UEVENT
+
+extern int dm_uevent_init(void);
+extern void dm_uevent_exit(void);
+extern void dm_send_uevents(struct list_head *events, struct kobject *kobj);
+extern void dm_path_uevent(enum dm_uevent_type event_type,
+			   struct dm_target *ti, const char *path,
+			   unsigned int nr_valid_paths);
+
+#else
+
+static inline int dm_uevent_init(void)
+{
+	return 0;
+}
+static inline void dm_uevent_exit(void)
+{
+}
+static inline void dm_send_uevents(struct list_head *events,
+				   struct kobject *kobj)
+{
+}
+static inline void dm_path_uevent(enum dm_uevent_type event_type,
+				  struct dm_target *ti, const char *path,
+				  unsigned int nr_valid_paths)
+{
+}
+
+#endif	/* CONFIG_DM_UEVENT */
+
+#endif	/* DM_UEVENT_H */