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, 20 insertions, 0 deletions

diff --git a/fs/befs/datastream.h b/fs/befs/datastream.h
new file mode 100644
index 000000000..39b1d4766
--- /dev/null
+++ b/fs/befs/datastream.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * datastream.h
+ *
+ */
+
+struct buffer_head *befs_read_datastream(struct super_block *sb,
+					 const befs_data_stream *ds,
+					 befs_off_t pos, uint *off);
+
+int befs_fblock2brun(struct super_block *sb, const befs_data_stream *data,
+		     befs_blocknr_t fblock, befs_block_run *run);
+
+size_t befs_read_lsymlink(struct super_block *sb, const befs_data_stream *data,
+			  void *buff, befs_off_t len);
+
+befs_blocknr_t befs_count_blocks(struct super_block *sb,
+			  const befs_data_stream *ds);
+
+extern const befs_inode_addr BAD_IADDR;