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, 32 insertions, 0 deletions

diff --git a/scripts/makelst b/scripts/makelst
new file mode 100755
index 000000000..e432af073
--- /dev/null
+++ b/scripts/makelst
@@ -0,0 +1,32 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# A script to dump mixed source code & assembly
+# with correct relocations from System.map
+# Requires the following lines in makefile:
+#%.lst: %.c
+#	$(CC) $(c_flags) -g -c -o $*.o $< &&
+#	$(srctree)/scripts/makelst $*.o System.map $(OBJDUMP) > $@
+#
+# Copyright (C) 2000 IBM Corporation
+# Author(s): DJ Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
+#            William Stearns <wstearns@pobox.com>
+#
+
+# awk style field access
+field() {
+  shift $1 ; echo $1
+}
+
+t1=`$3 --syms $1 | grep .text | grep -m1 " F "`
+if [ -n "$t1" ]; then
+  t2=`field 6 $t1`
+  if [ ! -r $2 ]; then
+    echo "No System.map" >&2
+  else
+    t3=`grep $t2 $2`
+    t4=`field 1 $t3`
+    t5=`field 1 $t1`
+    t6=`printf "%lu" $((0x$t4 - 0x$t5))`
+  fi
+fi
+$3 -r --source --adjust-vma=${t6:-0} $1