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, 78 insertions, 0 deletions

diff --git a/fs/gfs2/meta_io.h b/fs/gfs2/meta_io.h
new file mode 100644
index 000000000..ec76215bf
--- /dev/null
+++ b/fs/gfs2/meta_io.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
+ */
+
+#ifndef __DIO_DOT_H__
+#define __DIO_DOT_H__
+
+#include <linux/buffer_head.h>
+#include <linux/string.h>
+#include "incore.h"
+
+static inline void gfs2_buffer_clear(struct buffer_head *bh)
+{
+	memset(bh->b_data, 0, bh->b_size);
+}
+
+static inline void gfs2_buffer_clear_tail(struct buffer_head *bh, int head)
+{
+	BUG_ON(head > bh->b_size);
+	memset(bh->b_data + head, 0, bh->b_size - head);
+}
+
+static inline void gfs2_buffer_copy_tail(struct buffer_head *to_bh,
+					 int to_head,
+					 struct buffer_head *from_bh,
+					 int from_head)
+{
+	BUG_ON(from_head < to_head);
+	memcpy(to_bh->b_data + to_head, from_bh->b_data + from_head,
+	       from_bh->b_size - from_head);
+	memset(to_bh->b_data + to_bh->b_size + to_head - from_head,
+	       0, from_head - to_head);
+}
+
+extern const struct address_space_operations gfs2_meta_aops;
+extern const struct address_space_operations gfs2_rgrp_aops;
+
+static inline struct gfs2_sbd *gfs2_mapping2sbd(struct address_space *mapping)
+{
+	struct inode *inode = mapping->host;
+	if (mapping->a_ops == &gfs2_meta_aops) {
+		struct gfs2_glock_aspace *gla =
+			container_of(mapping, struct gfs2_glock_aspace, mapping);
+		return glock_sbd(&gla->glock);
+	} else
+		return inode->i_sb->s_fs_info;
+}
+
+struct buffer_head *gfs2_meta_new(struct gfs2_glock *gl, u64 blkno);
+int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags,
+		   int rahead, struct buffer_head **bhp);
+int gfs2_meta_wait(struct gfs2_sbd *sdp, struct buffer_head *bh);
+struct buffer_head *gfs2_getbuf(struct gfs2_glock *gl, u64 blkno,
+			        int create);
+enum {
+	REMOVE_JDATA = 0,
+	REMOVE_META = 1,
+};
+
+void gfs2_journal_wipe(struct gfs2_inode *ip, u64 bstart, u32 blen);
+int gfs2_meta_buffer(struct gfs2_inode *ip, u32 mtype, u64 num,
+		     struct buffer_head **bhp);
+
+static inline int gfs2_meta_inode_buffer(struct gfs2_inode *ip,
+					 struct buffer_head **bhp)
+{
+	return gfs2_meta_buffer(ip, GFS2_METATYPE_DI, ip->i_no_addr, bhp);
+}
+
+struct buffer_head *gfs2_meta_ra(struct gfs2_glock *gl, u64 dblock, u32 extlen);
+
+#define buffer_busy(bh) \
+((bh)->b_state & ((1ul << BH_Dirty) | (1ul << BH_Lock) | (1ul << BH_Pinned)))
+
+#endif /* __DIO_DOT_H__ */
+