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, 83 insertions, 0 deletions

diff --git a/fs/btrfs/tree-checker.h b/fs/btrfs/tree-checker.h
new file mode 100644
index 000000000..833e2fd98
--- /dev/null
+++ b/fs/btrfs/tree-checker.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Qu Wenruo 2017.  All rights reserved.
+ */
+
+#ifndef BTRFS_TREE_CHECKER_H
+#define BTRFS_TREE_CHECKER_H
+
+#include <linux/types.h>
+#include <uapi/linux/btrfs_tree.h>
+
+struct extent_buffer;
+struct btrfs_fs_info;
+struct btrfs_chunk;
+struct btrfs_key;
+
+/* All the extra info needed to verify the parentness of a tree block. */
+struct btrfs_tree_parent_check {
+	/*
+	 * The owner check against the tree block.
+	 *
+	 * Can be 0 to skip the owner check.
+	 */
+	u64 owner_root;
+
+	/*
+	 * Expected transid, can be 0 to skip the check, but such skip
+	 * should only be utilized for backref walk related code.
+	 */
+	u64 transid;
+
+	/*
+	 * The expected first key.
+	 *
+	 * This check can be skipped if @has_first_key is false, such skip
+	 * can happen for case where we don't have the parent node key,
+	 * e.g. reading the tree root, doing backref walk.
+	 */
+	struct btrfs_key first_key;
+	bool has_first_key;
+
+	/* The expected level. Should always be set. */
+	u8 level;
+};
+
+enum btrfs_tree_block_status {
+	BTRFS_TREE_BLOCK_CLEAN,
+	BTRFS_TREE_BLOCK_INVALID_NRITEMS,
+	BTRFS_TREE_BLOCK_INVALID_PARENT_KEY,
+	BTRFS_TREE_BLOCK_BAD_KEY_ORDER,
+	BTRFS_TREE_BLOCK_INVALID_LEVEL,
+	BTRFS_TREE_BLOCK_INVALID_FREE_SPACE,
+	BTRFS_TREE_BLOCK_INVALID_OFFSETS,
+	BTRFS_TREE_BLOCK_INVALID_BLOCKPTR,
+	BTRFS_TREE_BLOCK_INVALID_ITEM,
+	BTRFS_TREE_BLOCK_INVALID_OWNER,
+	BTRFS_TREE_BLOCK_WRITTEN_NOT_SET,
+};
+
+
+#define BTRFS_BLOCK_GROUP_VALID	(BTRFS_BLOCK_GROUP_TYPE_MASK | \
+				 BTRFS_BLOCK_GROUP_PROFILE_MASK | \
+				 BTRFS_BLOCK_GROUP_REMAPPED)
+
+/*
+ * Exported simply for btrfs-progs which wants to have the
+ * btrfs_tree_block_status return codes.
+ */
+enum btrfs_tree_block_status __btrfs_check_leaf(struct extent_buffer *leaf);
+enum btrfs_tree_block_status __btrfs_check_node(struct extent_buffer *node);
+
+int btrfs_check_leaf(struct extent_buffer *leaf);
+int btrfs_check_node(struct extent_buffer *node);
+
+int btrfs_check_chunk_valid(const struct btrfs_fs_info *fs_info,
+			    const struct extent_buffer *leaf,
+			    const struct btrfs_chunk *chunk, u64 logical,
+			    u32 sectorsize);
+int btrfs_check_eb_owner(const struct extent_buffer *eb, u64 root_owner);
+int btrfs_verify_level_key(struct extent_buffer *eb,
+			   const struct btrfs_tree_parent_check *check);
+
+#endif