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, 52 insertions, 0 deletions

diff --git a/fs/xfs/xfs_exchrange.h b/fs/xfs/xfs_exchrange.h
new file mode 100644
index 000000000..bc1298aba
--- /dev/null
+++ b/fs/xfs/xfs_exchrange.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2020-2024 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#ifndef __XFS_EXCHRANGE_H__
+#define __XFS_EXCHRANGE_H__
+
+/* Update the mtime/cmtime of file1 and file2 */
+#define __XFS_EXCHANGE_RANGE_UPD_CMTIME1	(1ULL << 63)
+#define __XFS_EXCHANGE_RANGE_UPD_CMTIME2	(1ULL << 62)
+
+/* Freshness check required */
+#define __XFS_EXCHANGE_RANGE_CHECK_FRESH2	(1ULL << 61)
+
+#define XFS_EXCHANGE_RANGE_PRIV_FLAGS	(__XFS_EXCHANGE_RANGE_UPD_CMTIME1 | \
+					 __XFS_EXCHANGE_RANGE_UPD_CMTIME2 | \
+					 __XFS_EXCHANGE_RANGE_CHECK_FRESH2)
+
+struct xfs_exchrange {
+	struct file		*file1;
+	struct file		*file2;
+
+	loff_t			file1_offset;
+	loff_t			file2_offset;
+	u64			length;
+
+	u64			flags;	/* XFS_EXCHANGE_RANGE flags */
+
+	/* file2 metadata for freshness checks */
+	u64			file2_ino;
+	struct timespec64	file2_mtime;
+	struct timespec64	file2_ctime;
+	u32			file2_gen;
+};
+
+long xfs_ioc_exchange_range(struct file *file,
+		struct xfs_exchange_range __user *argp);
+long xfs_ioc_start_commit(struct file *file,
+		struct xfs_commit_range __user *argp);
+long xfs_ioc_commit_range(struct file *file,
+		struct xfs_commit_range __user	*argp);
+
+struct xfs_exchmaps_req;
+
+void xfs_exchrange_ilock(struct xfs_trans *tp, struct xfs_inode *ip1,
+		struct xfs_inode *ip2);
+void xfs_exchrange_iunlock(struct xfs_inode *ip1, struct xfs_inode *ip2);
+
+int xfs_exchrange_estimate(struct xfs_exchmaps_req *req);
+
+#endif /* __XFS_EXCHRANGE_H__ */