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, 49 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/cache.c b/arch/m68k/coldfire/cache.c
new file mode 100644
index 000000000..98ee89b87
--- /dev/null
+++ b/arch/m68k/coldfire/cache.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+/***************************************************************************/
+
+/*
+ *	cache.c -- general ColdFire Cache maintenance code
+ *
+ *	Copyright (C) 2010, Greg Ungerer (gerg@snapgear.com)
+ */
+
+/***************************************************************************/
+
+#include <linux/kernel.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+
+/***************************************************************************/
+#ifdef CACHE_PUSH
+/***************************************************************************/
+
+/*
+ *	Use cpushl to push all dirty cache lines back to memory.
+ *	Older versions of GAS don't seem to know how to generate the
+ *	ColdFire cpushl instruction... Oh well, bit stuff it for now.
+ */
+
+void mcf_cache_push(void)
+{
+	__asm__ __volatile__ (
+		"clrl	%%d0\n\t"
+		"1:\n\t"
+		"movel	%%d0,%%a0\n\t"
+		"2:\n\t"
+		".word	0xf468\n\t"
+		"addl	%0,%%a0\n\t"
+		"cmpl	%1,%%a0\n\t"
+		"blt	2b\n\t"
+		"addql	#1,%%d0\n\t"
+		"cmpil	%2,%%d0\n\t"
+		"bne	1b\n\t"
+		: /* No output */
+		: "i" (CACHE_LINE_SIZE),
+		  "i" (DCACHE_SIZE / CACHE_WAYS),
+		  "i" (CACHE_WAYS)
+		: "d0", "a0" );
+}
+
+/***************************************************************************/
+#endif /* CACHE_PUSH */
+/***************************************************************************/