[PATCH 11/11] Input: ims-pcu - fix potential infinite loop in CDC union descriptor parsing

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

The driver parses CDC union descriptors in ims_pcu_get_cdc_union_desc()
by iterating through the extra descriptor data. However, it does not
verify that the bLength of each descriptor is at least 2. A malicious
device could provide a descriptor with bLength = 0, leading to an
infinite loop in the driver.

Add a check to ensure bLength is at least 2 before proceeding with
parsing.

Fixes: 628329d52474 (Input: add IMS Passenger Control Unit driver)
Cc: stable@vger.kernel.org
Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/misc/ims-pcu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c
index 422b1be62303..a04dd3ea3a48 100644
--- a/drivers/input/misc/ims-pcu.c
+++ b/drivers/input/misc/ims-pcu.c
@@ -1678,8 +1678,9 @@ ims_pcu_get_cdc_union_desc(struct usb_interface *intf)
 	while (buflen >= sizeof(*union_desc)) {
 		union_desc = (struct usb_cdc_union_desc *)buf;
 
-		if (union_desc->bLength > buflen) {
-			dev_err(&intf->dev, "Too large descriptor\n");
+		if (union_desc->bLength < 2 || union_desc->bLength > buflen) {
+			dev_err(&intf->dev, "Invalid descriptor length: %d\n",
+				union_desc->bLength);
 			return NULL;
 		}
 
-- 
2.54.0.746.g67dd491aae-goog