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, 278 insertions, 0 deletions

diff --git a/drivers/input/touch-overlay.c b/drivers/input/touch-overlay.c
new file mode 100644
index 000000000..b9fd82c48
--- /dev/null
+++ b/drivers/input/touch-overlay.c
@@ -0,0 +1,278 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Helper functions for overlay objects on touchscreens
+ *
+ *  Copyright (c) 2023 Javier Carrasco <javier.carrasco@wolfvision.net>
+ */
+
+#include <linux/export.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touch-overlay.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/property.h>
+
+struct touch_overlay_segment {
+	struct list_head list;
+	u32 x_origin;
+	u32 y_origin;
+	u32 x_size;
+	u32 y_size;
+	u32 key;
+	bool pressed;
+	int slot;
+};
+
+static int touch_overlay_get_segment(struct fwnode_handle *segment_node,
+				     struct touch_overlay_segment *segment,
+				     struct input_dev *input)
+{
+	int error;
+
+	error = fwnode_property_read_u32(segment_node, "x-origin",
+					 &segment->x_origin);
+	if (error)
+		return error;
+
+	error = fwnode_property_read_u32(segment_node, "y-origin",
+					 &segment->y_origin);
+	if (error)
+		return error;
+
+	error = fwnode_property_read_u32(segment_node, "x-size",
+					 &segment->x_size);
+	if (error)
+		return error;
+
+	error = fwnode_property_read_u32(segment_node, "y-size",
+					 &segment->y_size);
+	if (error)
+		return error;
+
+	error = fwnode_property_read_u32(segment_node, "linux,code",
+					 &segment->key);
+	if (!error)
+		input_set_capability(input, EV_KEY, segment->key);
+	else if (error != -EINVAL)
+		return error;
+
+	return 0;
+}
+
+/**
+ * touch_overlay_map - map overlay objects from the device tree and set
+ * key capabilities if buttons are defined.
+ * @list: pointer to the list that will hold the segments
+ * @input: pointer to the already allocated input_dev
+ *
+ * Returns 0 on success and error number otherwise.
+ *
+ * If buttons are defined, key capabilities are set accordingly.
+ */
+int touch_overlay_map(struct list_head *list, struct input_dev *input)
+{
+	struct fwnode_handle *fw_segment;
+	struct device *dev = input->dev.parent;
+	struct touch_overlay_segment *segment;
+	int error;
+
+	struct fwnode_handle *overlay __free(fwnode_handle) =
+		device_get_named_child_node(dev, "touch-overlay");
+	if (!overlay)
+		return 0;
+
+	fwnode_for_each_available_child_node(overlay, fw_segment) {
+		segment = devm_kzalloc(dev, sizeof(*segment), GFP_KERNEL);
+		if (!segment) {
+			fwnode_handle_put(fw_segment);
+			return -ENOMEM;
+		}
+		error = touch_overlay_get_segment(fw_segment, segment, input);
+		if (error) {
+			fwnode_handle_put(fw_segment);
+			return error;
+		}
+		list_add_tail(&segment->list, list);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(touch_overlay_map);
+
+/**
+ * touch_overlay_get_touchscreen_abs - get abs size from the touchscreen area.
+ * @list: pointer to the list that holds the segments
+ * @x: horizontal abs
+ * @y: vertical abs
+ */
+void touch_overlay_get_touchscreen_abs(struct list_head *list, u16 *x, u16 *y)
+{
+	struct touch_overlay_segment *segment;
+	struct list_head *ptr;
+
+	list_for_each(ptr, list) {
+		segment = list_entry(ptr, struct touch_overlay_segment, list);
+		if (!segment->key) {
+			*x = segment->x_size - 1;
+			*y = segment->y_size - 1;
+			break;
+		}
+	}
+}
+EXPORT_SYMBOL(touch_overlay_get_touchscreen_abs);
+
+static bool touch_overlay_segment_event(struct touch_overlay_segment *seg,
+					struct input_mt_pos *pos)
+{
+	if (pos->x >= seg->x_origin && pos->x < (seg->x_origin + seg->x_size) &&
+	    pos->y >= seg->y_origin && pos->y < (seg->y_origin + seg->y_size))
+		return true;
+
+	return false;
+}
+
+/**
+ * touch_overlay_mapped_touchscreen - check if a touchscreen area is mapped
+ * @list: pointer to the list that holds the segments
+ *
+ * Returns true if a touchscreen area is mapped or false otherwise.
+ */
+bool touch_overlay_mapped_touchscreen(struct list_head *list)
+{
+	struct touch_overlay_segment *segment;
+	struct list_head *ptr;
+
+	list_for_each(ptr, list) {
+		segment = list_entry(ptr, struct touch_overlay_segment, list);
+		if (!segment->key)
+			return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL(touch_overlay_mapped_touchscreen);
+
+static bool touch_overlay_event_on_ts(struct list_head *list,
+				      struct input_mt_pos *pos)
+{
+	struct touch_overlay_segment *segment;
+	struct list_head *ptr;
+
+	list_for_each(ptr, list) {
+		segment = list_entry(ptr, struct touch_overlay_segment, list);
+		if (segment->key)
+			continue;
+
+		if (touch_overlay_segment_event(segment, pos)) {
+			pos->x -= segment->x_origin;
+			pos->y -= segment->y_origin;
+			return true;
+		}
+		/* ignore touch events outside the defined area */
+		return false;
+	}
+
+	return true;
+}
+
+static bool touch_overlay_button_event(struct input_dev *input,
+				       struct touch_overlay_segment *segment,
+				       struct input_mt_pos *pos, int slot)
+{
+	struct input_mt *mt = input->mt;
+	struct input_mt_slot *s = &mt->slots[slot];
+	bool button_contact = touch_overlay_segment_event(segment, pos);
+
+	if (segment->slot == slot && segment->pressed) {
+		/* sliding out of the button releases it */
+		if (!button_contact) {
+			input_report_key(input, segment->key, false);
+			segment->pressed = false;
+			/* keep available for a possible touch event */
+			return false;
+		}
+		/* ignore sliding on the button while pressed */
+		s->frame = mt->frame;
+		return true;
+	} else if (button_contact) {
+		input_report_key(input, segment->key, true);
+		s->frame = mt->frame;
+		segment->slot = slot;
+		segment->pressed = true;
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * touch_overlay_sync_frame - update the status of the segments and report
+ * buttons whose tracked slot is unused.
+ * @list: pointer to the list that holds the segments
+ * @input: pointer to the input device associated to the contact
+ */
+void touch_overlay_sync_frame(struct list_head *list, struct input_dev *input)
+{
+	struct touch_overlay_segment *segment;
+	struct input_mt *mt = input->mt;
+	struct input_mt_slot *s;
+	struct list_head *ptr;
+
+	list_for_each(ptr, list) {
+		segment = list_entry(ptr, struct touch_overlay_segment, list);
+		if (!segment->key)
+			continue;
+
+		s = &mt->slots[segment->slot];
+		if (!input_mt_is_used(mt, s) && segment->pressed) {
+			input_report_key(input, segment->key, false);
+			segment->pressed = false;
+		}
+	}
+}
+EXPORT_SYMBOL(touch_overlay_sync_frame);
+
+/**
+ * touch_overlay_process_contact - process contacts according to the overlay
+ * mapping. This function acts as a filter to release the calling driver
+ * from the contacts that are either related to overlay buttons or out of the
+ * overlay touchscreen area, if defined.
+ * @list: pointer to the list that holds the segments
+ * @input: pointer to the input device associated to the contact
+ * @pos: pointer to the contact position
+ * @slot: slot associated to the contact (0 if multitouch is not supported)
+ *
+ * Returns true if the contact was processed (reported for valid key events
+ * and dropped for contacts outside the overlay touchscreen area) or false
+ * if the contact must be processed by the caller. In that case this function
+ * shifts the (x,y) coordinates to the overlay touchscreen axis if required.
+ */
+bool touch_overlay_process_contact(struct list_head *list,
+				   struct input_dev *input,
+				   struct input_mt_pos *pos, int slot)
+{
+	struct touch_overlay_segment *segment;
+	struct list_head *ptr;
+
+	/*
+	 * buttons must be prioritized over overlay touchscreens to account for
+	 * overlappings e.g. a button inside the touchscreen area.
+	 */
+	list_for_each(ptr, list) {
+		segment = list_entry(ptr, struct touch_overlay_segment, list);
+		if (segment->key &&
+		    touch_overlay_button_event(input, segment, pos, slot))
+			return true;
+	}
+
+	/*
+	 * valid contacts on the overlay touchscreen are left for the client
+	 * to be processed/reported according to its (possibly) unique features.
+	 */
+	return !touch_overlay_event_on_ts(list, pos);
+}
+EXPORT_SYMBOL(touch_overlay_process_contact);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Helper functions for overlay objects on touch devices");