** Description changed:
- After upgrading from Ubuntu 24.04 (kernel 6.8) to Ubuntu 26.04.1 LTS
- (kernel 7.0.0-38-generic), the touchpad tap-to-click became unreliable:
- single-finger taps are frequently not registered, and double-tapping to
- open folders often takes several attempts. This worked perfectly on the
- previous 6.8 kernel.
+ Summary
+ -------
+ After upgrading to Ubuntu 26.04.1 LTS, the touchpad regressed on the
+ 7.0.0-38-generic kernel: single-finger taps are frequently not
+ registered, and double-tap-to-open typically needs several attempts.
+ Booting the previously-installed 6.8.0-146-generic kernel on the SAME
+ installation makes the touchpad work perfectly again. This is
+ kernel-specific to 7.0.0; userspace (libinput, GNOME) and all touchpad
+ settings are identical across both boots.
- Hardware: "FocalTechPS/2 FocalTech Touchpad" (isa0060/serio4),
- psmouse/focaltech driver.
+ Steps to reproduce
+ ------------------
+ 1. Boot 7.0.0-38-generic.
+ 2. Use the touchpad: tap to click, double-tap to open folders.
+ -> Taps are often missed; opening folders takes several attempts.
+ 3. Reboot and select 6.8.0-146-generic (Advanced options for Ubuntu).
+ 4. Repeat the same actions.
+ -> Touchpad works reliably, as it did before the upgrade.
- GNOME touchpad settings are at defaults (tap-to-click enabled,
- double-click 400 ms, click-method default), so this is not a
- configuration issue.
+ Expected
+ --------
+ Touchpad taps/double-taps work reliably on 7.0.0, as they do on 6.8.0-146.
- The kernel log shows this UBSAN splat repeating while using the
- touchpad:
+ Actual
+ ------
+ Tap detection is unreliable only on 7.0.0-38-generic.
- UBSAN: array-index-out-of-bounds in drivers/input/mouse/focaltech.c:222:17
- index -1 is out of range for type 'focaltech_finger_state [5]'
- Call Trace:
- focaltech_process_packet+0x4e1/0x560 [psmouse]
- focaltech_process_byte+0x23/0x30 [psmouse]
- psmouse_handle_byte+0x19/0x70 [psmouse]
- psmouse_receive_byte+0x8d/0x300 [psmouse]
+ Hardware
+ --------
+ Touchpad: "FocalTechPS/2 FocalTech Touchpad" (isa0060/serio4), psmouse
+ driver.
- This matches CVE-2026-80574 (focaltech input driver: a finger index of 0
- is decremented to -1 and used as an array offset), which is already fixed
- upstream by making the finger index variables unsigned. Please backport
- the fix to the Ubuntu 26.04 7.0.0 kernel.
+ Environment
+ -----------
+ Release: Ubuntu 26.04.1 LTS
+ Good kernel: 6.8.0-146-generic (touchpad reliable)
+ Bad kernel: 7.0.0-38-generic (touchpad unreliable)
+ GNOME touchpad settings are at defaults (tap-to-click enabled), so this
+ is not a configuration issue.
- Workaround: booting the still-installed 6.8.0-146-generic kernel restores
- correct touchpad behaviour.
+ Note (possibly unrelated)
+ -------------------------
+ A UBSAN array-index-out-of-bounds in drivers/input/mouse/focaltech.c:222
+ ("index -1 ... focaltech_finger_state[5]") is present in the kernel log.
+ However, it appears on BOTH 6.8.0-146 and 7.0.0-38 in similar amounts, so
+ it does not distinguish the working kernel from the broken one and may be
+ unrelated to this symptom. Mentioned only for completeness; I make no
+ claim that it is the cause.
+
+ Workaround
+ ----------
+ Boot 6.8.0-146-generic.
ProblemType: Bug
Release: Ubuntu 26.04.1 LTS
Affected kernel: 7.0.0-38-generic
Unaffected kernel: 6.8.0-146-generic
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-38-generic 7.0.0-38.38
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
- USER PID ACCESS COMMAND
- /dev/snd/controlC1: jose 10161 F.... wireplumber
- /dev/snd/controlC0: jose 10161 F.... wireplumber
- /dev/snd/seq: jose 10153 F.... pipewire
+ USER PID ACCESS COMMAND
+ /dev/snd/controlC1: jose 10161 F.... wireplumber
+ /dev/snd/controlC0: jose 10161 F.... wireplumber
+ /dev/snd/seq: jose 10153 F.... pipewire
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Sat Oct 10 10:04:21 2026
HibernationDevice: RESUME=UUID=33c9a6d3-1565-44a6-b0f8-a86a8e80d835
InstallationDate: Installed on 2015-03-26 (4215 days ago)
InstallationMedia: Ubuntu-GNOME 14.10 "Utopic Unicorn" - Release amd64
(20141022.1)
MachineType: ASUSTeK COMPUTER INC. UX303LAB
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-38-generic
root=UUID=93b239dc-6bd0-4aa5-8c7b-f58b1b09e7bd ro quiet
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-10-10 (0 days ago)
dmi.bios.date: 12/11/2014
dmi.bios.release: 5.6
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: UX303LAB.203
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UX303LAB
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias:
dmi:bvnAmericanMegatrendsInc.:bvrUX303LAB.203:bd12/11/2014:br5.6:svnASUSTeKCOMPUTERINC.:pnUX303LAB:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX303LAB:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:skuASUS-NotebookSKU:pfaUX:
dmi.product.family: UX
dmi.product.name: UX303LAB
dmi.product.sku: ASUS-NotebookSKU
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.
** Summary changed:
- focaltech: UBSAN array-index-out-of-bounds (finger index -1) in
focaltech_process_packet on 7.0.0-38-generic — touchpad taps unreliable
+ Touchpad regression on linux 7.0.0-38-generic: FocalTech PS/2 taps frequently
missed (works fine on 6.8.0-146-generic)
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https://bugs.launchpad.net/bugs/2170428
Title:
Touchpad regression on linux 7.0.0-38-generic: FocalTech PS/2 taps
frequently missed (works fine on 6.8.0-146-generic)
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