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/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
new file mode 100644
index 000000000..d4eeed450
--- /dev/null
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -0,0 +1,52 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  loader module
+#
+# Copyright (c) Siemens AG, 2012, 2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import os
+
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)) + "/scripts/gdb")
+
+try:
+    gdb.parse_and_eval("0")
+    gdb.execute("", to_string=True)
+except:
+    gdb.write("NOTE: gdb 7.2 or later required for Linux helper scripts to "
+              "work.\n")
+else:
+    import linux.constants
+    if linux.constants.LX_CONFIG_DEBUG_INFO_REDUCED:
+        raise gdb.GdbError("Reduced debug information will prevent GDB "
+                           "from having complete types.\n")
+    import linux.utils
+    import linux.symbols
+    import linux.modules
+    import linux.dmesg
+    import linux.tasks
+    import linux.config
+    import linux.cpus
+    import linux.lists
+    import linux.rbtree
+    import linux.proc
+    import linux.timerlist
+    import linux.clk
+    import linux.genpd
+    import linux.device
+    import linux.vfs
+    import linux.pgtable
+    import linux.radixtree
+    import linux.interrupts
+    import linux.mm
+    import linux.stackdepot
+    import linux.page_owner
+    import linux.slab
+    import linux.vmalloc
+    import linux.kasan