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, 94 insertions, 0 deletions

diff --git a/drivers/dca/dca-sysfs.c b/drivers/dca/dca-sysfs.c
new file mode 100644
index 000000000..b915c2b46
--- /dev/null
+++ b/drivers/dca/dca-sysfs.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright(c) 2007 - 2009 Intel Corporation. All rights reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/device.h>
+#include <linux/idr.h>
+#include <linux/kdev_t.h>
+#include <linux/err.h>
+#include <linux/dca.h>
+#include <linux/gfp.h>
+#include <linux/export.h>
+
+static const struct class dca_class = {
+	.name = "dca",
+};
+static struct idr dca_idr;
+static spinlock_t dca_idr_lock;
+
+int dca_sysfs_add_req(struct dca_provider *dca, struct device *dev, int slot)
+{
+	struct device *cd;
+	static int req_count;
+
+	cd = device_create(&dca_class, dca->cd, MKDEV(0, slot + 1), NULL,
+			   "requester%d", req_count++);
+	return PTR_ERR_OR_ZERO(cd);
+}
+
+void dca_sysfs_remove_req(struct dca_provider *dca, int slot)
+{
+	device_destroy(&dca_class, MKDEV(0, slot + 1));
+}
+
+int dca_sysfs_add_provider(struct dca_provider *dca, struct device *dev)
+{
+	struct device *cd;
+	int ret;
+
+	idr_preload(GFP_KERNEL);
+	spin_lock(&dca_idr_lock);
+
+	ret = idr_alloc(&dca_idr, dca, 0, 0, GFP_NOWAIT);
+	if (ret >= 0)
+		dca->id = ret;
+
+	spin_unlock(&dca_idr_lock);
+	idr_preload_end();
+	if (ret < 0)
+		return ret;
+
+	cd = device_create(&dca_class, dev, MKDEV(0, 0), NULL, "dca%d", dca->id);
+	if (IS_ERR(cd)) {
+		spin_lock(&dca_idr_lock);
+		idr_remove(&dca_idr, dca->id);
+		spin_unlock(&dca_idr_lock);
+		return PTR_ERR(cd);
+	}
+	dca->cd = cd;
+	return 0;
+}
+
+void dca_sysfs_remove_provider(struct dca_provider *dca)
+{
+	device_unregister(dca->cd);
+	dca->cd = NULL;
+	spin_lock(&dca_idr_lock);
+	idr_remove(&dca_idr, dca->id);
+	spin_unlock(&dca_idr_lock);
+}
+
+int __init dca_sysfs_init(void)
+{
+	int err;
+
+	idr_init(&dca_idr);
+	spin_lock_init(&dca_idr_lock);
+
+	err = class_register(&dca_class);
+	if (err) {
+		idr_destroy(&dca_idr);
+		return err;
+	}
+	return 0;
+}
+
+void __exit dca_sysfs_exit(void)
+{
+	class_unregister(&dca_class);
+	idr_destroy(&dca_idr);
+}
+