[PATCH 7.1 10/21] Input: rmi4 - fix num_subpackets overflow in register descriptor

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>

commit 2b4b482d5c4c23c668b998a7da985aea0fa4a978 upstream.

RMI_REG_DESC_SUBPACKET_BITS is defined as 296 (37 * BITS_PER_BYTE). This
may overflow num_subpackets in struct rmi_register_desc_item which is
defined as a u8.

Fix this by changing the type of num_subpackets to u16.

Fixes: 2b6a321da9a2 ("Input: synaptics-rmi4 - add support for Synaptics RMI4 devices")
Cc: stable@vger.kernel.org
Assisted-by: Gemini:gemini-3.1-pro
Link: https://patch.msgid.link/20260505045952.1570713-4-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/input/rmi4/rmi_driver.h |    2 +-
 drivers/input/rmi4/rmi_f12.c    |    7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/input/rmi4/rmi_driver.h
+++ b/drivers/input/rmi4/rmi_driver.h
@@ -53,7 +53,7 @@ struct pdt_entry {
 struct rmi_register_desc_item {
 	u16 reg;
 	unsigned long reg_size;
-	u8 num_subpackets;
+	u16 num_subpackets;
 	unsigned long subpacket_map[BITS_TO_LONGS(
 				RMI_REG_DESC_SUBPACKET_BITS)];
 };
--- a/drivers/input/rmi4/rmi_f12.c
+++ b/drivers/input/rmi4/rmi_f12.c
@@ -467,6 +467,13 @@ static int rmi_f12_probe(struct rmi_func
 		f12->data1 = item;
 		f12->data1_offset = data_offset;
 		data_offset += item->reg_size;
+
+		if (item->num_subpackets > 255) {
+			dev_err(&fn->dev, "Too many fingers declared: %d\n",
+				item->num_subpackets);
+			return -EINVAL;
+		}
+
 		sensor->nbr_fingers = item->num_subpackets;
 		sensor->report_abs = 1;
 		sensor->attn_size += item->reg_size;