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, 107 insertions, 0 deletions

diff --git a/fs/btrfs/tree-log.h b/fs/btrfs/tree-log.h
new file mode 100644
index 000000000..81ab5eeeb
--- /dev/null
+++ b/fs/btrfs/tree-log.h
@@ -0,0 +1,107 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2008 Oracle.  All rights reserved.
+ */
+
+#ifndef BTRFS_TREE_LOG_H
+#define BTRFS_TREE_LOG_H
+
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/fscrypt.h>
+#include "transaction.h"
+
+enum btrfs_log_mode {
+	/* Log everything about an inode. */
+	LOG_INODE_ALL,
+	/* Log just enough to recreate the inode during log replay. */
+	LOG_INODE_EXISTS,
+};
+
+struct inode;
+struct dentry;
+struct btrfs_ordered_extent;
+struct btrfs_root;
+struct btrfs_trans_handle;
+
+/* return value for btrfs_log_dentry_safe that means we don't need to log it at all */
+#define BTRFS_NO_LOG_SYNC 256
+
+/*
+ * We can't use the tree log for whatever reason, force a transaction commit.
+ * We use a negative value because there are functions through the logging code
+ * that need to return an error (< 0 value), false (0) or true (1). Any negative
+ * value will do, as it will cause the log to be marked for a full sync.
+ */
+#define BTRFS_LOG_FORCE_COMMIT				(-(MAX_ERRNO + 1))
+
+struct btrfs_log_ctx {
+	int log_ret;
+	int log_transid;
+	bool log_new_dentries;
+	bool logging_new_name;
+	bool logging_new_delayed_dentries;
+	/* Indicate if the inode being logged was logged before. */
+	bool logged_before;
+	struct btrfs_inode *inode;
+	struct list_head list;
+	/* Only used for fast fsyncs. */
+	struct list_head ordered_extents;
+	struct list_head conflict_inodes;
+	int num_conflict_inodes;
+	bool logging_conflict_inodes;
+	/*
+	 * Used for fsyncs that need to copy items from the subvolume tree to
+	 * the log tree (full sync flag set or copy everything flag set) to
+	 * avoid allocating a temporary extent buffer while holding a lock on
+	 * an extent buffer of the subvolume tree and under the log transaction.
+	 * Also helps to avoid allocating and freeing a temporary extent buffer
+	 * in case we need to process multiple leaves from the subvolume tree.
+	 */
+	struct extent_buffer *scratch_eb;
+};
+
+void btrfs_init_log_ctx(struct btrfs_log_ctx *ctx, struct btrfs_inode *inode);
+void btrfs_init_log_ctx_scratch_eb(struct btrfs_log_ctx *ctx);
+void btrfs_release_log_ctx_extents(struct btrfs_log_ctx *ctx);
+
+static inline void btrfs_set_log_full_commit(struct btrfs_trans_handle *trans)
+{
+	WRITE_ONCE(trans->fs_info->last_trans_log_full_commit, trans->transid);
+}
+
+static inline int btrfs_need_log_full_commit(struct btrfs_trans_handle *trans)
+{
+	return READ_ONCE(trans->fs_info->last_trans_log_full_commit) ==
+		trans->transid;
+}
+
+int btrfs_sync_log(struct btrfs_trans_handle *trans,
+		   struct btrfs_root *root, struct btrfs_log_ctx *ctx);
+void btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root);
+void btrfs_free_log_root_tree(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info);
+int btrfs_recover_log_trees(struct btrfs_root *tree_root);
+int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
+			  struct dentry *dentry,
+			  struct btrfs_log_ctx *ctx);
+void btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans,
+				  const struct fscrypt_str *name,
+				  struct btrfs_inode *dir, u64 index);
+void btrfs_del_inode_ref_in_log(struct btrfs_trans_handle *trans,
+				const struct fscrypt_str *name,
+				struct btrfs_inode *inode,
+				struct btrfs_inode *dir);
+void btrfs_end_log_trans(struct btrfs_root *root);
+void btrfs_pin_log_trans(struct btrfs_root *root);
+void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans,
+			     struct btrfs_inode *dir, struct btrfs_inode *inode,
+			     bool for_rename);
+void btrfs_record_snapshot_destroy(struct btrfs_trans_handle *trans,
+				   struct btrfs_inode *dir);
+void btrfs_record_new_subvolume(const struct btrfs_trans_handle *trans,
+				struct btrfs_inode *dir);
+void btrfs_log_new_name(struct btrfs_trans_handle *trans,
+			struct dentry *old_dentry, struct btrfs_inode *old_dir,
+			u64 old_dir_index, struct dentry *parent);
+
+#endif