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, 47 insertions, 0 deletions

diff --git a/fs/nilfs2/btnode.h b/fs/nilfs2/btnode.h
new file mode 100644
index 000000000..4bc5612df
--- /dev/null
+++ b/fs/nilfs2/btnode.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS B-tree node cache
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Seiji Kihara.
+ * Revised by Ryusuke Konishi.
+ */
+
+#ifndef _NILFS_BTNODE_H
+#define _NILFS_BTNODE_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/backing-dev.h>
+
+/**
+ * struct nilfs_btnode_chkey_ctxt - change key context
+ * @oldkey: old key of block's moving content
+ * @newkey: new key for block's content
+ * @bh: buffer head of old buffer
+ * @newbh: buffer head of new buffer
+ */
+struct nilfs_btnode_chkey_ctxt {
+	__u64 oldkey;
+	__u64 newkey;
+	struct buffer_head *bh;
+	struct buffer_head *newbh;
+};
+
+void nilfs_init_btnc_inode(struct inode *btnc_inode);
+void nilfs_btnode_cache_clear(struct address_space *);
+struct buffer_head *nilfs_btnode_create_block(struct address_space *btnc,
+					      __u64 blocknr);
+int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t,
+			      blk_opf_t, struct buffer_head **, sector_t *);
+void nilfs_btnode_delete(struct buffer_head *);
+int nilfs_btnode_prepare_change_key(struct address_space *,
+				    struct nilfs_btnode_chkey_ctxt *);
+void nilfs_btnode_commit_change_key(struct address_space *,
+				    struct nilfs_btnode_chkey_ctxt *);
+void nilfs_btnode_abort_change_key(struct address_space *,
+				   struct nilfs_btnode_chkey_ctxt *);
+
+#endif	/* _NILFS_BTNODE_H */