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, 57 insertions, 0 deletions

diff --git a/fs/btrfs/dir-item.h b/fs/btrfs/dir-item.h
new file mode 100644
index 000000000..e52174a8b
--- /dev/null
+++ b/fs/btrfs/dir-item.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_DIR_ITEM_H
+#define BTRFS_DIR_ITEM_H
+
+#include <linux/types.h>
+#include <linux/crc32c.h>
+
+struct fscrypt_str;
+struct btrfs_fs_info;
+struct btrfs_key;
+struct btrfs_path;
+struct btrfs_inode;
+struct btrfs_root;
+struct btrfs_trans_handle;
+
+int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir_ino,
+			  const struct fscrypt_str *name);
+int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
+			  const struct fscrypt_str *name, struct btrfs_inode *dir,
+			  const struct btrfs_key *location, u8 type, u64 index);
+struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
+					     struct btrfs_root *root,
+					     struct btrfs_path *path, u64 dir,
+					     const struct fscrypt_str *name, int mod);
+struct btrfs_dir_item *btrfs_lookup_dir_index_item(
+			struct btrfs_trans_handle *trans,
+			struct btrfs_root *root,
+			struct btrfs_path *path, u64 dir,
+			u64 index, const struct fscrypt_str *name, int mod);
+struct btrfs_dir_item *btrfs_search_dir_index_item(struct btrfs_root *root,
+			    struct btrfs_path *path, u64 dirid,
+			    const struct fscrypt_str *name);
+int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
+			      struct btrfs_root *root,
+			      struct btrfs_path *path,
+			      const struct btrfs_dir_item *di);
+int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
+			    struct btrfs_root *root,
+			    struct btrfs_path *path, u64 objectid,
+			    const char *name, u16 name_len,
+			    const void *data, u16 data_len);
+struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
+					  struct btrfs_root *root,
+					  struct btrfs_path *path, u64 dir,
+					  const char *name, u16 name_len,
+					  int mod);
+struct btrfs_dir_item *btrfs_match_dir_item_name(const struct btrfs_path *path,
+						 const char *name,
+						 int name_len);
+
+static inline u64 btrfs_name_hash(const char *name, int len)
+{
+       return crc32c((u32)~1, name, len);
+}
+
+#endif