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, 202 insertions, 0 deletions

diff --git a/sound/usb/6fire/comm.c b/sound/usb/6fire/comm.c
new file mode 100644
index 000000000..d3b7cab85
--- /dev/null
+++ b/sound/usb/6fire/comm.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux driver for TerraTec DMX 6Fire USB
+ *
+ * Device communications
+ *
+ * Author:	Torsten Schenk <torsten.schenk@zoho.com>
+ * Created:	Jan 01, 2011
+ * Copyright:	(C) Torsten Schenk
+ */
+
+#include "comm.h"
+#include "chip.h"
+#include "midi.h"
+
+enum {
+	COMM_EP = 1,
+	COMM_FPGA_EP = 2
+};
+
+static void usb6fire_comm_init_urb(struct comm_runtime *rt, struct urb *urb,
+		u8 *buffer, void *context, void(*handler)(struct urb *urb))
+{
+	usb_init_urb(urb);
+	urb->transfer_buffer = buffer;
+	urb->pipe = usb_sndintpipe(rt->chip->dev, COMM_EP);
+	urb->complete = handler;
+	urb->context = context;
+	urb->interval = 1;
+	urb->dev = rt->chip->dev;
+}
+
+static void usb6fire_comm_receiver_handler(struct urb *urb)
+{
+	struct comm_runtime *rt = urb->context;
+	struct midi_runtime *midi_rt = rt->chip->midi;
+
+	if (!urb->status) {
+		u8 len = rt->receiver_buffer[1];
+
+		if (rt->receiver_buffer[0] == 0x10 && /* midi in event */
+		    len <= COMM_RECEIVER_BUFSIZE - 2 &&
+		    urb->actual_length >= len + 2)
+			if (midi_rt)
+				midi_rt->in_received(midi_rt,
+						rt->receiver_buffer + 2, len);
+	}
+
+	if (!rt->chip->shutdown) {
+		urb->status = 0;
+		urb->actual_length = 0;
+		if (usb_submit_urb(urb, GFP_ATOMIC) < 0)
+			dev_warn(&urb->dev->dev,
+					"comm data receiver aborted.\n");
+	}
+}
+
+static void usb6fire_comm_init_buffer(u8 *buffer, u8 id, u8 request,
+		u8 reg, u8 vl, u8 vh)
+{
+	buffer[0] = 0x01;
+	buffer[2] = request;
+	buffer[3] = id;
+	switch (request) {
+	case 0x02:
+		buffer[1] = 0x05; /* length (starting at buffer[2]) */
+		buffer[4] = reg;
+		buffer[5] = vl;
+		buffer[6] = vh;
+		break;
+
+	case 0x12:
+		buffer[1] = 0x0b; /* length (starting at buffer[2]) */
+		buffer[4] = 0x00;
+		buffer[5] = 0x18;
+		buffer[6] = 0x05;
+		buffer[7] = 0x00;
+		buffer[8] = 0x01;
+		buffer[9] = 0x00;
+		buffer[10] = 0x9e;
+		buffer[11] = reg;
+		buffer[12] = vl;
+		break;
+
+	case 0x20:
+	case 0x21:
+	case 0x22:
+		buffer[1] = 0x04;
+		buffer[4] = reg;
+		buffer[5] = vl;
+		break;
+	}
+}
+
+static int usb6fire_comm_send_buffer(u8 *buffer, struct usb_device *dev)
+{
+	int ret;
+	int actual_len;
+
+	ret = usb_interrupt_msg(dev, usb_sndintpipe(dev, COMM_EP),
+			buffer, buffer[1] + 2, &actual_len, 1000);
+	if (ret < 0)
+		return ret;
+	else if (actual_len != buffer[1] + 2)
+		return -EIO;
+	return 0;
+}
+
+static int usb6fire_comm_write8(struct comm_runtime *rt, u8 request,
+		u8 reg, u8 value)
+{
+	u8 *buffer;
+	int ret;
+
+	/* 13: maximum length of message */
+	buffer = kmalloc(13, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	usb6fire_comm_init_buffer(buffer, 0x00, request, reg, value, 0x00);
+	ret = usb6fire_comm_send_buffer(buffer, rt->chip->dev);
+
+	kfree(buffer);
+	return ret;
+}
+
+static int usb6fire_comm_write16(struct comm_runtime *rt, u8 request,
+		u8 reg, u8 vl, u8 vh)
+{
+	u8 *buffer;
+	int ret;
+
+	/* 13: maximum length of message */
+	buffer = kmalloc(13, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	usb6fire_comm_init_buffer(buffer, 0x00, request, reg, vl, vh);
+	ret = usb6fire_comm_send_buffer(buffer, rt->chip->dev);
+
+	kfree(buffer);
+	return ret;
+}
+
+int usb6fire_comm_init(struct sfire_chip *chip)
+{
+	struct comm_runtime *rt = kzalloc_obj(struct comm_runtime);
+	struct urb *urb;
+	int ret;
+
+	if (!rt)
+		return -ENOMEM;
+
+	rt->receiver_buffer = kzalloc(COMM_RECEIVER_BUFSIZE, GFP_KERNEL);
+	if (!rt->receiver_buffer) {
+		kfree(rt);
+		return -ENOMEM;
+	}
+
+	urb = &rt->receiver;
+	rt->serial = 1;
+	rt->chip = chip;
+	usb_init_urb(urb);
+	rt->init_urb = usb6fire_comm_init_urb;
+	rt->write8 = usb6fire_comm_write8;
+	rt->write16 = usb6fire_comm_write16;
+
+	/* submit an urb that receives communication data from device */
+	urb->transfer_buffer = rt->receiver_buffer;
+	urb->transfer_buffer_length = COMM_RECEIVER_BUFSIZE;
+	urb->pipe = usb_rcvintpipe(chip->dev, COMM_EP);
+	urb->dev = chip->dev;
+	urb->complete = usb6fire_comm_receiver_handler;
+	urb->context = rt;
+	urb->interval = 1;
+	ret = usb_submit_urb(urb, GFP_KERNEL);
+	if (ret < 0) {
+		kfree(rt->receiver_buffer);
+		kfree(rt);
+		dev_err(&chip->dev->dev, "cannot create comm data receiver.");
+		return ret;
+	}
+	chip->comm = rt;
+	return 0;
+}
+
+void usb6fire_comm_abort(struct sfire_chip *chip)
+{
+	struct comm_runtime *rt = chip->comm;
+
+	if (rt)
+		usb_poison_urb(&rt->receiver);
+}
+
+void usb6fire_comm_destroy(struct sfire_chip *chip)
+{
+	struct comm_runtime *rt = chip->comm;
+
+	kfree(rt->receiver_buffer);
+	kfree(rt);
+	chip->comm = NULL;
+}