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, 44 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/flush.h b/drivers/md/dm-vdo/flush.h
new file mode 100644
index 000000000..97252d665
--- /dev/null
+++ b/drivers/md/dm-vdo/flush.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#ifndef VDO_FLUSH_H
+#define VDO_FLUSH_H
+
+#include "funnel-workqueue.h"
+#include "types.h"
+#include "vio.h"
+#include "wait-queue.h"
+
+/* A marker for tracking which journal entries are affected by a flush request. */
+struct vdo_flush {
+	/* The completion for enqueueing this flush request. */
+	struct vdo_completion completion;
+	/* The flush bios covered by this request */
+	struct bio_list bios;
+	/* The wait queue entry for this flush */
+	struct vdo_waiter waiter;
+	/* Which flush this struct represents */
+	sequence_number_t flush_generation;
+};
+
+struct flusher;
+
+int __must_check vdo_make_flusher(struct vdo *vdo);
+
+void vdo_free_flusher(struct flusher *flusher);
+
+thread_id_t __must_check vdo_get_flusher_thread_id(struct flusher *flusher);
+
+void vdo_complete_flushes(struct flusher *flusher);
+
+void vdo_dump_flusher(const struct flusher *flusher);
+
+void vdo_launch_flush(struct vdo *vdo, struct bio *bio);
+
+void vdo_drain_flusher(struct flusher *flusher, struct vdo_completion *completion);
+
+void vdo_resume_flusher(struct flusher *flusher, struct vdo_completion *parent);
+
+#endif /* VDO_FLUSH_H */