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, 31 insertions, 0 deletions

diff --git a/fs/btrfs/xattr.h b/fs/btrfs/xattr.h
new file mode 100644
index 000000000..0ce10e4ec
--- /dev/null
+++ b/fs/btrfs/xattr.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2007 Red Hat.  All rights reserved.
+ */
+
+#ifndef BTRFS_XATTR_H
+#define BTRFS_XATTR_H
+
+#include <linux/types.h>
+
+struct dentry;
+struct inode;
+struct qstr;
+struct xattr_handler;
+struct btrfs_trans_handle;
+
+extern const struct xattr_handler * const btrfs_xattr_handlers[];
+
+int btrfs_getxattr(const struct inode *inode, const char *name,
+		void *buffer, size_t size);
+int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode,
+		   const char *name, const void *value, size_t size, int flags);
+int btrfs_setxattr_trans(struct inode *inode, const char *name,
+			 const void *value, size_t size, int flags);
+ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size);
+
+int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
+				     struct inode *inode, struct inode *dir,
+				     const struct qstr *qstr);
+
+#endif