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, 50 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/reset.c b/arch/m68k/coldfire/reset.c
new file mode 100644
index 000000000..6e5f8ab39
--- /dev/null
+++ b/arch/m68k/coldfire/reset.c
@@ -0,0 +1,50 @@
+/*
+ * reset.c  -- common ColdFire SoC reset support
+ *
+ * (C) Copyright 2012, Greg Ungerer <gerg@uclinux.org>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <asm/machdep.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+
+/*
+ *	There are 2 common methods amongst the ColdFure parts for reseting
+ *	the CPU. But there are couple of exceptions, the 5272 and the 547x
+ *	have something completely special to them, and we let their specific
+ *	subarch code handle them.
+ */
+
+#ifdef MCFSIM_SYPCR
+static void mcf_cpu_reset(void)
+{
+	local_irq_disable();
+	/* Set watchdog to soft reset, and enabled */
+	mcf_write8(0xc0, MCFSIM_SYPCR);
+	for (;;)
+		/* wait for watchdog to timeout */;
+}
+#endif
+
+#ifdef MCF_RCR
+static void mcf_cpu_reset(void)
+{
+	local_irq_disable();
+	mcf_write8(MCF_RCR_SWRESET, MCF_RCR);
+}
+#endif
+
+static int __init mcf_setup_reset(void)
+{
+	mach_reset = mcf_cpu_reset;
+	return 0;
+}
+
+arch_initcall(mcf_setup_reset);