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, 54 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/mxl5xx.h b/drivers/media/dvb-frontends/mxl5xx.h
new file mode 100644
index 000000000..139e16b2e
--- /dev/null
+++ b/drivers/media/dvb-frontends/mxl5xx.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Driver for the MaxLinear MxL5xx family of tuners/demods
+ *
+ * Copyright (C) 2014-2015 Ralph Metzler <rjkm@metzlerbros.de>
+ *                         Marcus Metzler <mocm@metzlerbros.de>
+ *                         developed for Digital Devices GmbH
+ *
+ * based on code:
+ * Copyright (c) 2011-2013 MaxLinear, Inc. All rights reserved
+ * which was released under GPL V2
+ */
+
+#ifndef _MXL5XX_H_
+#define _MXL5XX_H_
+
+#include <linux/types.h>
+#include <linux/i2c.h>
+
+#include <media/dvb_frontend.h>
+
+struct mxl5xx_cfg {
+	u8   adr;
+	u8   type;
+	u32  cap;
+	u32  clk;
+	u32  ts_clk;
+
+	u8  *fw;
+	u32  fw_len;
+
+	int (*fw_read)(void *priv, u8 *buf, u32 len);
+	void *fw_priv;
+};
+
+#if IS_REACHABLE(CONFIG_DVB_MXL5XX)
+
+extern struct dvb_frontend *mxl5xx_attach(struct i2c_adapter *i2c,
+	struct mxl5xx_cfg *cfg, u32 demod, u32 tuner,
+	int (**fn_set_input)(struct dvb_frontend *, int));
+
+#else
+
+static inline struct dvb_frontend *mxl5xx_attach(struct i2c_adapter *i2c,
+	struct mxl5xx_cfg *cfg, u32 demod, u32 tuner,
+	int (**fn_set_input)(struct dvb_frontend *, int))
+{
+	pr_warn("%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+
+#endif /* CONFIG_DVB_MXL5XX */
+
+#endif /* _MXL5XX_H_ */