From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B628C3E3175 for ; Tue, 14 Jul 2026 14:54:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784040876; cv=none; b=FOteKDufLV8aZBExn4Jk97H05kayfKyO4uFprLYv5UpcML7Nn+E2iLtCZe1hu7ZD/4lFNGP4lKBSH1VCT5EJHeokV34xBI0bTIoYm2+SRGMPMr4vkVItBf6+JY67W9tY4t81tkQatK+rE7R6C98S+SyC630HzTK0vrArPK3yidM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784040876; c=relaxed/simple; bh=3Y1WmfuqdZgiLA6U+xQXJdTJxpdyyLe9Sl87nmfwRJY=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=q2Q2dniRXvTcO94XR3Ee8Wx4vx7sTV2GasSeFfSKM50pD40MhzyVjD1pEdWPN5MjvTyh8OfBEZgoR0+PJ2oKnQETh5qYAGi5S5Qgi7GJ9HJksqLWmaCqROAmbzSWe8WsAc1mrclH5fztNRI7Tt1e3KT47HXueMwUwIcCzF6vcD8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bpUj+N6R; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bpUj+N6R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 281491F000E9; Tue, 14 Jul 2026 14:54:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784040874; bh=vYo8jdeHKzJMIbOWEJLW/Rvbhj5wwDLDA34uGP3DYJM=; h=Subject:To:Cc:From:Date; b=bpUj+N6RLRIfkqWiK3jJIRsOYxyrHDJ7HtuPfCnELO/Rfvv50qPa0dn/7h0gQIbuZ RO/E0ckka2iOZmOfRolvSh1dKnqlRXMmHZUHFlxlNI5mHxcyRwdyY5FL0topD3qK0I cp57xywElpTFSyEpK+TWFKZyX3avhZH4OmmCPyM4= Subject: FAILED: patch "[PATCH] HID: multitouch: fix out-of-bounds bit access on mt_io_flags" failed to apply to 6.6-stable tree To: trungnh@cystack.net,bentiss@kernel.org Cc: From: Date: Tue, 14 Jul 2026 16:54:18 +0200 Message-ID: <2026071417-praising-reconvene-e068@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 8813b0612275cc61fe9e6603d0ee019247ade6be # git commit -s git send-email --to '' --in-reply-to '2026071417-praising-reconvene-e068@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8813b0612275cc61fe9e6603d0ee019247ade6be Mon Sep 17 00:00:00 2001 From: Trung Nguyen Date: Thu, 2 Jul 2026 00:13:19 +0700 Subject: [PATCH] HID: multitouch: fix out-of-bounds bit access on mt_io_flags 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 diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c index 0495152091e3..edb37b4c867e 100644 --- a/drivers/hid/hid-multitouch.c +++ b/drivers/hid/hid-multitouch.c @@ -31,6 +31,7 @@ * [1] https://gitlab.freedesktop.org/libevdev/hid-tools */ +#include #include #include #include @@ -97,8 +98,7 @@ enum report_mode { TOUCHPAD_REPORT_ALL = TOUCHPAD_REPORT_BUTTONS | TOUCHPAD_REPORT_CONTACTS, }; -#define MT_IO_SLOTS_MASK GENMASK(7, 0) /* reserve first 8 bits for slot tracking */ -#define MT_IO_FLAGS_RUNNING 32 +#define MT_IO_FLAGS_RUNNING 0 static const bool mtrue = true; /* default for true */ static const bool mfalse; /* default for false */ @@ -174,10 +174,9 @@ struct mt_device { struct timer_list release_timer; /* to release sticky fingers */ struct hid_haptic_device *haptic; /* haptic related configuration */ struct hid_device *hdev; /* hid_device we're attached to */ - unsigned long mt_io_flags; /* mt flags (MT_IO_FLAGS_RUNNING) - * first 8 bits are reserved for keeping the slot - * states, this is fine because we only support up - * to 250 slots (MT_MAX_MAXCONTACT) + unsigned long mt_io_flags; /* mt flags (MT_IO_FLAGS_RUNNING) */ + unsigned long *active_slots; /* bitmap of slots with an active + * contact, sized for maxcontacts */ __u8 inputmode_value; /* InputMode HID feature value */ __u8 maxcontacts; @@ -1036,7 +1035,7 @@ static void mt_release_pending_palms(struct mt_device *td, for_each_set_bit(slotnum, app->pending_palm_slots, td->maxcontacts) { clear_bit(slotnum, app->pending_palm_slots); - clear_bit(slotnum, &td->mt_io_flags); + clear_bit(slotnum, td->active_slots); input_mt_slot(input, slotnum); input_mt_report_slot_inactive(input); @@ -1247,9 +1246,9 @@ static int mt_process_slot(struct mt_device *td, struct input_dev *input, input_event(input, EV_ABS, ABS_MT_TOUCH_MAJOR, major); input_event(input, EV_ABS, ABS_MT_TOUCH_MINOR, minor); - set_bit(slotnum, &td->mt_io_flags); + set_bit(slotnum, td->active_slots); } else { - clear_bit(slotnum, &td->mt_io_flags); + clear_bit(slotnum, td->active_slots); } return 0; @@ -1384,7 +1383,7 @@ static void mt_touch_report(struct hid_device *hid, * defect. */ if (app->quirks & MT_QUIRK_STICKY_FINGERS) { - if (td->mt_io_flags & MT_IO_SLOTS_MASK) + if (!bitmap_empty(td->active_slots, td->maxcontacts)) mod_timer(&td->release_timer, jiffies + msecs_to_jiffies(100)); else @@ -1443,6 +1442,15 @@ static int mt_touch_input_configured(struct hid_device *hdev, if (td->is_pressurepad) __set_bit(INPUT_PROP_PRESSUREPAD, input->propbit); + if (!td->active_slots) { + td->active_slots = devm_kcalloc(&td->hdev->dev, + BITS_TO_LONGS(td->maxcontacts), + sizeof(long), + GFP_KERNEL); + if (!td->active_slots) + return -ENOMEM; + } + app->pending_palm_slots = devm_kcalloc(&hi->input->dev, BITS_TO_LONGS(td->maxcontacts), sizeof(long), @@ -2062,7 +2070,7 @@ static void mt_release_contacts(struct hid_device *hid) for (i = 0; i < mt->num_slots; i++) { input_mt_slot(input_dev, i); input_mt_report_slot_inactive(input_dev); - clear_bit(i, &td->mt_io_flags); + clear_bit(i, td->active_slots); } input_mt_sync_frame(input_dev); input_sync(input_dev); @@ -2085,7 +2093,7 @@ static void mt_expired_timeout(struct timer_list *t) */ if (test_and_set_bit_lock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags)) return; - if (td->mt_io_flags & MT_IO_SLOTS_MASK) + if (!bitmap_empty(td->active_slots, td->maxcontacts)) mt_release_contacts(hdev); clear_bit_unlock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags); }