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, 69 insertions, 0 deletions

diff --git a/fs/xfs/xfs_itable.h b/fs/xfs/xfs_itable.h
new file mode 100644
index 000000000..2d0612f14
--- /dev/null
+++ b/fs/xfs/xfs_itable.h
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2000-2001 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+#ifndef __XFS_ITABLE_H__
+#define	__XFS_ITABLE_H__
+
+/* In-memory representation of a userspace request for batch inode data. */
+struct xfs_ibulk {
+	struct xfs_mount	*mp;
+	struct mnt_idmap	*idmap;
+	void __user		*ubuffer; /* user output buffer */
+	xfs_ino_t		startino; /* start with this inode */
+	unsigned int		icount;   /* number of elements in ubuffer */
+	unsigned int		ocount;   /* number of records returned */
+	unsigned int		flags;    /* XFS_IBULK_FLAG_* */
+	unsigned int		iwalk_flags; /* XFS_IWALK_FLAG_* */
+};
+
+/* Fill out the bs_extents64 field if set. */
+#define XFS_IBULK_NREXT64	(1U << 0)
+
+/* Signal that we can return metadata directories. */
+#define XFS_IBULK_METADIR	(1U << 1)
+
+/*
+ * Advance the user buffer pointer by one record of the given size.  If the
+ * buffer is now full, return the appropriate error code.
+ */
+static inline int
+xfs_ibulk_advance(
+	struct xfs_ibulk	*breq,
+	size_t			bytes)
+{
+	char __user		*b = breq->ubuffer;
+
+	breq->ubuffer = b + bytes;
+	breq->ocount++;
+	return breq->ocount == breq->icount ? -ECANCELED : 0;
+}
+
+/*
+ * Return stat information in bulk (by-inode) for the filesystem.
+ */
+
+/*
+ * Return codes for the formatter function are 0 to continue iterating, and
+ * non-zero to stop iterating.  Any non-zero value will be passed up to the
+ * bulkstat/inumbers caller.  The special value -ECANCELED can be used to stop
+ * iteration, as neither bulkstat nor inumbers will ever generate that error
+ * code on their own.
+ */
+
+typedef int (*bulkstat_one_fmt_pf)(struct xfs_ibulk *breq,
+		const struct xfs_bulkstat *bstat);
+
+int xfs_bulkstat_one(struct xfs_ibulk *breq, bulkstat_one_fmt_pf formatter);
+int xfs_bulkstat(struct xfs_ibulk *breq, bulkstat_one_fmt_pf formatter);
+void xfs_bulkstat_to_bstat(struct xfs_mount *mp, struct xfs_bstat *bs1,
+		const struct xfs_bulkstat *bstat);
+
+typedef int (*inumbers_fmt_pf)(struct xfs_ibulk *breq,
+		const struct xfs_inumbers *igrp);
+
+int xfs_inumbers(struct xfs_ibulk *breq, inumbers_fmt_pf formatter);
+void xfs_inumbers_to_inogrp(struct xfs_inogrp *ig1,
+		const struct xfs_inumbers *ig);
+
+#endif	/* __XFS_ITABLE_H__ */