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, 45 insertions, 0 deletions

diff --git a/drivers/gpu/host1x/channel.h b/drivers/gpu/host1x/channel.h
new file mode 100644
index 000000000..d7aede204
--- /dev/null
+++ b/drivers/gpu/host1x/channel.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Tegra host1x Channel
+ *
+ * Copyright (c) 2010-2013, NVIDIA Corporation.
+ */
+
+#ifndef __HOST1X_CHANNEL_H
+#define __HOST1X_CHANNEL_H
+
+#include <linux/io.h>
+#include <linux/kref.h>
+#include <linux/mutex.h>
+
+#include "cdma.h"
+
+struct host1x;
+struct host1x_channel;
+
+struct host1x_channel_list {
+	struct host1x_channel *channels;
+
+	struct mutex lock;
+	unsigned long *allocated_channels;
+};
+
+struct host1x_channel {
+	struct kref refcount;
+	unsigned int id;
+	struct mutex submitlock;
+	void __iomem *regs;
+	struct host1x_client *client;
+	struct device *dev;
+	struct host1x_cdma cdma;
+};
+
+/* channel list operations */
+int host1x_channel_list_init(struct host1x_channel_list *chlist,
+			     unsigned int num_channels);
+void host1x_channel_list_free(struct host1x_channel_list *chlist);
+struct host1x_channel *host1x_channel_get_index(struct host1x *host,
+						unsigned int index);
+void host1x_channel_stop_all(struct host1x *host);
+
+#endif