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, 95 insertions, 0 deletions

diff --git a/net/devres.c b/net/devres.c
new file mode 100644
index 000000000..5ccf6ca31
--- /dev/null
+++ b/net/devres.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This file contains all networking devres helpers.
+ */
+
+#include <linux/device.h>
+#include <linux/etherdevice.h>
+#include <linux/netdevice.h>
+
+struct net_device_devres {
+	struct net_device *ndev;
+};
+
+static void devm_free_netdev(struct device *dev, void *this)
+{
+	struct net_device_devres *res = this;
+
+	free_netdev(res->ndev);
+}
+
+struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
+					   unsigned int txqs, unsigned int rxqs)
+{
+	struct net_device_devres *dr;
+
+	dr = devres_alloc(devm_free_netdev, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return NULL;
+
+	dr->ndev = alloc_etherdev_mqs(sizeof_priv, txqs, rxqs);
+	if (!dr->ndev) {
+		devres_free(dr);
+		return NULL;
+	}
+
+	devres_add(dev, dr);
+
+	return dr->ndev;
+}
+EXPORT_SYMBOL(devm_alloc_etherdev_mqs);
+
+static void devm_unregister_netdev(struct device *dev, void *this)
+{
+	struct net_device_devres *res = this;
+
+	unregister_netdev(res->ndev);
+}
+
+static int netdev_devres_match(struct device *dev, void *this, void *match_data)
+{
+	struct net_device_devres *res = this;
+	struct net_device *ndev = match_data;
+
+	return ndev == res->ndev;
+}
+
+/**
+ *	devm_register_netdev - resource managed variant of register_netdev()
+ *	@dev: managing device for this netdev - usually the parent device
+ *	@ndev: device to register
+ *
+ *	This is a devres variant of register_netdev() for which the unregister
+ *	function will be called automatically when the managing device is
+ *	detached. Note: the net_device used must also be resource managed by
+ *	the same struct device.
+ */
+int devm_register_netdev(struct device *dev, struct net_device *ndev)
+{
+	struct net_device_devres *dr;
+	int ret;
+
+	/* struct net_device must itself be managed. For now a managed netdev
+	 * can only be allocated by devm_alloc_etherdev_mqs() so the check is
+	 * straightforward.
+	 */
+	if (WARN_ON(!devres_find(dev, devm_free_netdev,
+				 netdev_devres_match, ndev)))
+		return -EINVAL;
+
+	dr = devres_alloc(devm_unregister_netdev, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	ret = register_netdev(ndev);
+	if (ret) {
+		devres_free(dr);
+		return ret;
+	}
+
+	dr->ndev = ndev;
+	devres_add(ndev->dev.parent, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_register_netdev);