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, 68 insertions, 0 deletions

diff --git a/arch/m68k/sun3/dvma.c b/arch/m68k/sun3/dvma.c
new file mode 100644
index 000000000..83fcae6a0
--- /dev/null
+++ b/arch/m68k/sun3/dvma.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/arch/m68k/sun3/dvma.c
+ *
+ * Written by Sam Creasey
+ *
+ * Sun3 IOMMU routines used for dvma accesses.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/memblock.h>
+#include <linux/list.h>
+#include <asm/page.h>
+#include <asm/sun3mmu.h>
+#include <asm/dvma.h>
+
+
+static unsigned long ptelist[120];
+
+static unsigned long dvma_page(unsigned long kaddr, unsigned long vaddr)
+{
+	unsigned long pte;
+	unsigned long j;
+	pte_t ptep;
+
+	j = *(volatile unsigned long *)kaddr;
+	*(volatile unsigned long *)kaddr = j;
+
+	ptep = pfn_pte(virt_to_pfn((void *)kaddr), PAGE_KERNEL);
+	pte = pte_val(ptep);
+//	pr_info("dvma_remap: addr %lx -> %lx pte %08lx\n", kaddr, vaddr, pte);
+	if(ptelist[(vaddr & 0xff000) >> PAGE_SHIFT] != pte) {
+		sun3_put_pte(vaddr, pte);
+		ptelist[(vaddr & 0xff000) >> PAGE_SHIFT] = pte;
+	}
+
+	return (vaddr + (kaddr & ~PAGE_MASK));
+
+}
+
+int dvma_map_iommu(unsigned long kaddr, unsigned long baddr,
+			      int len)
+{
+
+	unsigned long end;
+	unsigned long vaddr;
+
+	vaddr = dvma_btov(baddr);
+
+	end = vaddr + len;
+
+	while(vaddr < end) {
+		dvma_page(kaddr, vaddr);
+		kaddr += PAGE_SIZE;
+		vaddr += PAGE_SIZE;
+	}
+
+	return 0;
+
+}
+
+void __init sun3_dvma_init(void)
+{
+	memset(ptelist, 0, sizeof(ptelist));
+}