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, 43 insertions, 0 deletions

diff --git a/arch/mips/dec/reset.c b/arch/mips/dec/reset.c
new file mode 100644
index 000000000..ee1ad38f4
--- /dev/null
+++ b/arch/mips/dec/reset.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Reset a DECstation machine.
+ *
+ * Copyright (C) 199x  the Anonymous
+ * Copyright (C) 2001, 2002, 2003  Maciej W. Rozycki
+ */
+#include <linux/interrupt.h>
+#include <linux/linkage.h>
+
+#include <asm/addrspace.h>
+
+#include <asm/dec/reset.h>
+
+typedef void __noreturn (* noret_func_t)(void);
+
+static inline void __noreturn back_to_prom(void)
+{
+	noret_func_t func = (void *)CKSEG1ADDR(0x1fc00000);
+
+	func();
+}
+
+void __noreturn dec_machine_restart(char *command)
+{
+	back_to_prom();
+}
+
+void __noreturn dec_machine_halt(void)
+{
+	back_to_prom();
+}
+
+void __noreturn dec_machine_power_off(void)
+{
+    /* DECstations don't have a software power switch */
+	back_to_prom();
+}
+
+irqreturn_t dec_intr_halt(int irq, void *dev_id)
+{
+	dec_machine_halt();
+}