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, 61 insertions, 0 deletions

diff --git a/fs/xfs/scrub/trace.c b/fs/xfs/scrub/trace.c
new file mode 100644
index 000000000..e5efc6806
--- /dev/null
+++ b/fs/xfs/scrub/trace.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2017-2023 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#include "xfs_platform.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_inode.h"
+#include "xfs_btree.h"
+#include "xfs_ag.h"
+#include "xfs_rtbitmap.h"
+#include "xfs_quota.h"
+#include "xfs_quota_defs.h"
+#include "xfs_da_format.h"
+#include "xfs_dir2.h"
+#include "xfs_rmap.h"
+#include "xfs_parent.h"
+#include "xfs_metafile.h"
+#include "xfs_rtgroup.h"
+#include "xfs_trans.h"
+#include "scrub/scrub.h"
+#include "scrub/xfile.h"
+#include "scrub/xfarray.h"
+#include "scrub/quota.h"
+#include "scrub/iscan.h"
+#include "scrub/orphanage.h"
+#include "scrub/nlinks.h"
+#include "scrub/fscounters.h"
+#include "scrub/bitmap.h"
+#include "scrub/ino_bitmap.h"
+#include "scrub/xfblob.h"
+#include "scrub/dirtree.h"
+
+/* Figure out which block the btree cursor was pointing to. */
+static inline xfs_fsblock_t
+xchk_btree_cur_fsbno(
+	struct xfs_btree_cur	*cur,
+	int			level)
+{
+	if (level < cur->bc_nlevels && cur->bc_levels[level].bp)
+		return XFS_DADDR_TO_FSB(cur->bc_mp,
+				xfs_buf_daddr(cur->bc_levels[level].bp));
+
+	if (level == cur->bc_nlevels - 1 &&
+	    cur->bc_ops->type == XFS_BTREE_TYPE_INODE)
+		return XFS_INODE_TO_FSB(cur->bc_ino.ip);
+
+	return NULLFSBLOCK;
+}
+
+/*
+ * We include this last to have the helpers above available for the trace
+ * event implementations.
+ */
+#define CREATE_TRACE_POINTS
+#include "scrub/trace.h"