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/fs/xfs/scrub/dabtree.h b/fs/xfs/scrub/dabtree.h
new file mode 100644
index 000000000..de291e3b7
--- /dev/null
+++ b/fs/xfs/scrub/dabtree.h
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2017-2023 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#ifndef __XFS_SCRUB_DABTREE_H__
+#define __XFS_SCRUB_DABTREE_H__
+
+/* dir/attr btree */
+
+struct xchk_da_btree {
+	struct xfs_da_args	dargs;
+	xfs_dahash_t		hashes[XFS_DA_NODE_MAXDEPTH];
+	int			maxrecs[XFS_DA_NODE_MAXDEPTH];
+	struct xfs_da_state	*state;
+	struct xfs_scrub	*sc;
+	void			*private;
+
+	/*
+	 * Lowest and highest directory block address in which we expect
+	 * to find dir/attr btree node blocks.  For a directory this
+	 * (presumably) means between LEAF_OFFSET and FREE_OFFSET; for
+	 * attributes there is no limit.
+	 */
+	xfs_dablk_t		lowest;
+	xfs_dablk_t		highest;
+
+	int			tree_level;
+};
+
+typedef int (*xchk_da_btree_rec_fn)(struct xchk_da_btree *ds, int level);
+
+/* Check for da btree operation errors. */
+bool xchk_da_process_error(struct xchk_da_btree *ds, int level, int *error);
+
+/* Check for da btree corruption. */
+void xchk_da_set_corrupt(struct xchk_da_btree *ds, int level);
+void xchk_da_set_preen(struct xchk_da_btree *ds, int level);
+
+void xchk_da_set_preen(struct xchk_da_btree *ds, int level);
+
+int xchk_da_btree_hash(struct xchk_da_btree *ds, int level, __be32 *hashp);
+int xchk_da_btree(struct xfs_scrub *sc, int whichfork,
+		xchk_da_btree_rec_fn scrub_fn, void *private);
+
+#endif /* __XFS_SCRUB_DABTREE_H__ */