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, 133 insertions, 0 deletions

diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
new file mode 100644
index 000000000..303ed6c71
--- /dev/null
+++ b/fs/btrfs/bio.h
@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ * Copyright (C) 2022 Christoph Hellwig.
+ */
+
+#ifndef BTRFS_BIO_H
+#define BTRFS_BIO_H
+
+#include <linux/types.h>
+#include <linux/bio.h>
+#include <linux/workqueue.h>
+#include "tree-checker.h"
+
+struct btrfs_bio;
+struct btrfs_fs_info;
+struct btrfs_inode;
+
+#define BTRFS_BIO_INLINE_CSUM_SIZE	64
+
+typedef void (*btrfs_bio_end_io_t)(struct btrfs_bio *bbio);
+
+/*
+ * Highlevel btrfs I/O structure.  It is allocated by btrfs_bio_alloc and
+ * passed to btrfs_submit_bbio() for mapping to the physical devices.
+ */
+struct btrfs_bio {
+	/*
+	 * Inode and offset into it that this I/O operates on.
+	 *
+	 * If the inode is a data one, csum verification and read-repair
+	 * will be done automatically.
+	 * If the inode is a metadata one, everything is handled by the caller.
+	 */
+	struct btrfs_inode *inode;
+	u64 file_offset;
+
+	union {
+		/*
+		 * For data reads: checksumming and original I/O information.
+		 * (for internal use in the btrfs_submit_bbio() machinery only)
+		 */
+		struct {
+			u8 *csum;
+			u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE];
+			struct bvec_iter saved_iter;
+		};
+
+		/*
+		 * For data writes:
+		 * - ordered extent covering the bio
+		 * - pointer to the checksums for this bio
+		 * - original physical address from the allocator
+		 *   (for zone append only)
+		 * - original logical address, used for checksumming fscrypt bios
+		 */
+		struct {
+			struct btrfs_ordered_extent *ordered;
+			struct btrfs_ordered_sum *sums;
+			struct work_struct csum_work;
+			struct completion csum_done;
+			struct bvec_iter csum_saved_iter;
+			u64 orig_physical;
+			u64 orig_logical;
+		};
+
+		/* For metadata reads: parentness verification. */
+		struct btrfs_tree_parent_check parent_check;
+	};
+
+	/* For internal use in read end I/O handling */
+	struct work_struct end_io_work;
+
+	/* End I/O information supplied to btrfs_bio_alloc */
+	btrfs_bio_end_io_t end_io;
+	void *private;
+
+	atomic_t pending_ios;
+	u16 mirror_num;
+
+	/* Save the first error status of split bio. */
+	blk_status_t status;
+
+	/* Use the commit root to look up csums (data read bio only). */
+	bool csum_search_commit_root:1;
+
+	/*
+	 * Since scrub will reuse btree inode, we need this flag to distinguish
+	 * scrub bios.
+	 */
+	bool is_scrub:1;
+
+	/* Whether the bio is coming from copy_remapped_data_io(). */
+	bool is_remap:1;
+
+	/* Whether the csum generation for data write is async. */
+	bool async_csum:1;
+
+	/* Whether the bio is written using zone append. */
+	bool can_use_append:1;
+
+	/*
+	 * This member must come last, bio_alloc_bioset will allocate enough
+	 * bytes for entire btrfs_bio but relies on bio being last.
+	 */
+	struct bio bio;
+};
+
+static inline struct btrfs_bio *btrfs_bio(struct bio *bio)
+{
+	return container_of(bio, struct btrfs_bio, bio);
+}
+
+int __init btrfs_bioset_init(void);
+void __cold btrfs_bioset_exit(void);
+
+void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_inode *inode, u64 file_offset,
+		    btrfs_bio_end_io_t end_io, void *private);
+struct btrfs_bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
+				  struct btrfs_inode *inode, u64 file_offset,
+				  btrfs_bio_end_io_t end_io, void *private);
+void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status);
+
+/* Submit using blkcg_punt_bio_submit. */
+#define REQ_BTRFS_CGROUP_PUNT			REQ_FS_PRIVATE
+
+void btrfs_submit_bbio(struct btrfs_bio *bbio, int mirror_num);
+void btrfs_submit_repair_write(struct btrfs_bio *bbio, int mirror_num, bool dev_replace);
+int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 fileoff,
+			    u32 length, u64 logical, const phys_addr_t paddrs[],
+			    unsigned int step, int mirror_num);
+
+#endif