kernel/git/stable/linux.git/drivers/hid/hid-multitouch.c, branch master

HID: multitouch: fix out-of-bounds bit access on mt_io_flags

2026-07-01T18:36:12+00:00

mt_io_flags is a single unsigned long, but mt_process_slot(), mt_release_pending_palms() and mt_release_contacts() use it as a per-slot bitmap indexed by the slot number. That slot number is only bounded by td->maxcontacts, which is taken from the device's ContactCountMaximum feature report and can be up to 255, not by BITS_PER_LONG. As a result, a multitouch device that advertises a large contact count makes set_bit()/clear_bit() operate past the mt_io_flags word and corrupt the adjacent members of struct mt_device. The sticky-fingers release timer is the easiest way to reach this. mt_release_contacts() runs for (i = 0; i < mt->num_slots; i++) clear_bit(i, &td->mt_io_flags); with num_slots == maxcontacts. For maxcontacts around 250 the loop clears the bits that overlap td->applications.next, zeroing that list head, and the list_for_each_entry() that immediately follows then dereferences NULL. The kernel panics from timer (softirq) context. On a KASAN build this shows up as a general protection fault in mt_release_contacts() with a null-ptr-deref at offset 0x58, which is offsetof(struct mt_application, num_received). The state is reachable from an untrusted USB or Bluetooth HID multitouch device; no local privileges are required. Store the per-slot active state in a separately allocated bitmap sized for maxcontacts, the same pattern already used for pending_palm_slots, and keep only MT_IO_FLAGS_RUNNING in mt_io_flags. The two "mt_io_flags & MT_IO_SLOTS_MASK" arming checks become bitmap_empty(td->active_slots, td->maxcontacts). Move MT_IO_FLAGS_RUNNING back to bit 0. It was bumped to bit 32 by the same commit to leave the low byte for the slot bits; with the slot bits gone it fits in bit 0 again, which also keeps it within the unsigned long on 32-bit. Fixes: 46f781e0d151 ("HID: multitouch: fix sticky fingers") Cc: stable@vger.kernel.org Signed-off-by: Trung Nguyen Signed-off-by: Benjamin Tissoires

Merge branch 'for-7.2/multitouch' into for-linus

2026-06-16T19:52:21+00:00

- UX improvement fixes for Yoga Book 9 (Dave Carey)

HID: multitouch: Honor ContactCount for Yoga Book 9 to suppress ghost contacts

2026-06-10T16:28:19+00:00

The INGENIC 17EF:6161 firmware on the Lenovo Yoga Book 9 14IAH10 does not clear stale contact slots when fingers are lifted. Each HID report contains up to 10 finger slots, but only the first ContactCount slots represent valid contacts; the remaining slots retain TipSwitch=1 with positions from previous touches. Raw HID capture confirms this: across a 60-second capture with repeated multi-finger gestures, 90% of frames had more TipSwitch=1 slots than the reported ContactCount. The ContactCount field itself is always accurate. Add MT_QUIRK_CONTACT_CNT_ACCURATE to the MT_CLS_YOGABOOK9I class so the driver stops processing slots once ContactCount valid contacts have been consumed, discarding the stale ghost entries per HID specification section 17. MT_QUIRK_NOT_SEEN_MEANS_UP (already in the class) ensures that any slot skipped by this guard is released via INPUT_MT_DROP_UNUSED at frame sync. Signed-off-by: Dave Carey Tested-by: Dave Carey Signed-off-by: Jiri Kosina

HID: pass the buffer size to hid_report_raw_event

2026-05-12T16:03:37+00:00

commit 0a3fe972a7cb ("HID: core: Mitigate potential OOB by removing bogus memset()") enforced the provided data to be at least the size of the declared buffer in the report descriptor to prevent a buffer overflow. However, we can try to be smarter by providing both the buffer size and the data size, meaning that hid_report_raw_event() can make better decision whether we should plaining reject the buffer (buffer overflow attempt) or if we can safely memset it to 0 and pass it to the rest of the stack. Fixes: 0a3fe972a7cb ("HID: core: Mitigate potential OOB by removing bogus memset()") Cc: stable@vger.kernel.org Signed-off-by: Benjamin Tissoires Acked-by: Johan Hovold Reviewed-by: Greg Kroah-Hartman Signed-off-by: Jiri Kosina

HID: multitouch: Fix Yoga Book 9 14IAH10 touchscreen misclassification

2026-05-12T15:39:26+00:00

The Lenovo Yoga Book 9 14IAH10 (83KJ) (17EF:6161) firmware includes a HID_DG_TOUCHPAD application collection designed for the Windows inbox HID driver's Win8 PTP touchpad mode. On Linux the HID_DG_TOUCHSCREEN collections provide the correct direct-touch interface. The presence of the touchpad collection causes hid-multitouch to misclassify the touchscreen nodes as indirect buttonpads, leaving them non-functional. Within the touchpad collection: - HID_UP_BUTTON usages trigger the touchscreen-with-buttons heuristic that sets INPUT_MT_POINTER on the touchscreen applications. - The HID_DG_TOUCHPAD application itself sets INPUT_MT_POINTER via mt_allocate_application(), propagating to all touchscreen nodes. - A HID_DG_BUTTONTYPE feature (report 0x51) returns MT_BUTTONTYPE_CLICKPAD, setting td->is_buttonpad = true for the entire device. Additionally, the firmware resets if any USB control request arrives while the CDC-ACM interface is initialising (~1.18 s after enumeration). The Win8 compliance blob (0xff00:0xc5) and Contact Count Max feature reports in the touchscreen collections trigger GET_REPORT calls at probe that hit this window. Surface Switch (0x57) and Button Switch (0x58) feature reports are sent by mt_set_modes() on every input-device open and close, repeatedly hitting this window throughout device lifetime. The firmware also leaves a persistent ghost contact in its contact buffer (contact ID 2, fixed coordinates, tip always asserted) on every enumeration. This ghost occupies a multitouch slot and prevents KWin from seeing a clean finger-lift, causing stuck touch state. The ghost is cleared when Input Mode is set via HID_REQ_SET_REPORT at probe. Fix using a report descriptor fixup in mt_report_fixup() and a class definition update: 1. Remove the entire HID_DG_TOUCHPAD application collection. Parsing HID short items from its header to the matching End Collection and closing the gap with memmove eliminates all three BUTTONPAD heuristics and the feature reports within the collection. 2. Neutralize the Win8 compliance blob feature reports remaining in the touchscreen collections by changing Usage Page 0xff00 to 0x0f00, preventing the case 0xff0000c5 branch in mt_feature_mapping() from issuing GET_REPORT. 3. Neutralize the Contact Count Max feature reports by changing usage 0x55 to 0x00; set maxcontacts = 10 in the class definition so the driver uses the correct contact limit without querying the device. 4. Neutralize Surface Switch (0x57) and Button Switch (0x58) feature report usages in the Device Configuration collection so mt_set_modes() does not issue HID_REQ_SET_REPORT for these on every input-device open/close. Input Mode (0x52) is intentionally left intact: the single HID_REQ_SET_REPORT at probe flushes the firmware's contact buffer and clears the persistent ghost contact. By probe time the cdc-acm driver has already satisfied the CDC-ACM init watchdog (~130 ms), so this request arrives safely after the reset window has closed. 5. Add MT_QUIRK_NOT_SEEN_MEANS_UP to the MT_CLS_YOGABOOK9I class so that contacts not present in a frame are released via INPUT_MT_DROP_UNUSED, preventing stale multitouch slots from lingering if the firmware omits a contact from a report. Signed-off-by: Dave Carey Tested-by: Dave Carey Signed-off-by: Jiri Kosina

HID: multitouch: Check to ensure report responses match the request

2026-03-17T10:36:16+00:00

It is possible for a malicious (or clumsy) device to respond to a specific report's feature request using a completely different report ID. This can cause confusion in the HID core resulting in nasty side-effects such as OOB writes. Add a check to ensure that the report ID in the response, matches the one that was requested. If it doesn't, omit reporting the raw event and return early. Signed-off-by: Lee Jones Signed-off-by: Benjamin Tissoires

HID: multitouch: Keep latency normal on deactivate for reactivation gesture

2026-02-26T16:10:22+00:00

Uniwill devices have a built in gesture in the touchpad to de- and reactivate it by double taping the upper left corner. This gesture stops working when latency is set to high, so this patch keeps the latency on normal. Cc: stable@vger.kernel.org Signed-off-by: Werner Sembach [jkosina@suse.com: change bit from 24 to 25] [jkosina@suse.com: update shortlog] Signed-off-by: Jiri Kosina

HID: multitouch: new class MT_CLS_EGALAX_P80H84

2026-02-24T08:41:21+00:00

Fixes: f9e82295eec1 ("HID: multitouch: add eGalaxTouch P80H84 support") Signed-off-by: Ian Ray Signed-off-by: Jiri Kosina

HID: multitouch: add eGalaxTouch EXC3188 support

2026-01-23T12:54:21+00:00

Add support for the for the EXC3188 touchscreen from eGalaxy. Signed-off-by: Thorsten Schmelzer Signed-off-by: Michael Tretter Signed-off-by: Jiri Kosina

HID: multitouch: add quirks for Lenovo Yoga Book 9i

2026-01-10T09:04:59+00:00

The Lenovo Yoga Book 9i is a dual-screen laptop, with a single composite USB device providing both touch and tablet interfaces for both screens. All inputs report through a single device, differentiated solely by report numbers. As there is no way for udev to differentiate the inputs based on USB vendor/product ID or interface numbers, custom naming is required to match against for downstream configuration. A firmware bug also results in an erroneous InRange message report being received after the stylus leaves proximity, blocking later touch events. Add required quirks for Gen 8 to Gen 10 models, including a new quirk providing for custom input device naming and dropping erroneous InRange reports. Signed-off-by: Brian Howard Tested-by: Brian Howard Tested-by: Kris Fredrick Reported-by: Andrei Shumailov Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220386 Signed-off-by: Jiri Kosina