Public bug reported:
Package: xorg-server
Distribution: Ubuntu 26.04.1 Long Term Support (LTS), resolute, amd64
Installed xserver-xorg-core: 2:21.1.22-1ubuntu1.2
Kernel: 7.0.0-38-generic, x86_64
Desktop: MATE, with LightDM 1.32.0-6ubuntu4
C library: libc6 2.43-2ubuntu2.4
pixman: 0.46.4
Integrated graphics: Intel Skylake/ULT, PCI device ID 1926, i915 kernel driver
Summary
-------
A Universal Serial Bus (USB) hub and its attached Jabra Evolve2 65 headset were
disconnected/switched. Immediately afterward, Xorg crashed with signal 11
(segmentation fault, SIGSEGV), terminating the graphical desktop session. The
user confirms the device-disconnection action. LightDM subsequently started a
replacement X server and greeter. The user rebooted to recover the working
desktop.
This is one observed occurrence of this specific sequence, not a
controlled reproduction. Device removal is the suspected trigger; the
exact defective callback/allocation is not established.
Steps associated with the observed failure
-----------------------------------------
1. Run a MATE desktop session under LightDM/Xorg.
2. Connect a Jabra Evolve2 65 through a USB hub. The headset exposes an input
interface as well as audio functionality.
3. Disconnect/switch the hub or attached headset.
Expected: Device removal should leave the display server and desktop session
running.
Actual: Xorg crashes and applications lose their display connection; the
desktop session ends.
Device information (generic product IDs only)
--------------------------------------------
USB hub: vendor:product 0a12:4010
Headset: Jabra Evolve2 65, vendor:product 0b0e:24b7
The headset was registered as a keyboard/input device through the kernel's
jabra Human Interface Device (HID) driver.
No device serial numbers are included.
Event sequence (relative times; host and account identifiers removed)
--------------------------------------------------------------------
t+0.000000 s: kernel: usb 1-3.1.4: USB disconnect, device number 11
t+0.006427 s: kernel: usb 1-3.1.4.1: USB disconnect, device number 13
t+approximately 0.107 s: a desktop component reports that display :0 cannot be
opened.
t+approximately 0.301 s: Apport is invoked for /usr/lib/xorg/Xorg after its
fatal signal handler aborts the server (signal 6).
t+approximately 0.309 s: Apport skips saving a new report because a previous
unseen Xorg report already exists.
t+0.363917 s: kernel records a segmentation fault in synergy-core, after the
display connection has already failed.
Approximately one second later: LightDM closes the desktop user session and
starts another X server and the login greeter.
Xorg fatal output (verbatim technical backtrace)
-----------------------------------------------
(EE) Backtrace:
(EE) unw_get_proc_name failed: no unwind info found [-10]
(EE) 0: /usr/lib/xorg/Xorg (?+0x0) [0x626f76f47634]
(EE) unw_get_proc_name failed: no unwind info found [-10]
(EE) 1: /usr/lib/x86_64-linux-gnu/libc.so.6 (?+0x0) [0x757057245cb0]
(EE) 2: /usr/lib/x86_64-linux-gnu/libc.so.6 (__GI_perror+0x39) [0x757057412ac8]
(EE) 3: /usr/lib/xorg/Xorg (WaitForSomething+0x195) [0x626f76f40305]
(EE) unw_get_proc_name failed: no unwind info found [-10]
(EE) 4: /usr/lib/xorg/Xorg (?+0x0) [0x626f76dbc08a]
(EE) unw_get_proc_name failed: no unwind info found [-10]
(EE) 5: /usr/lib/xorg/Xorg (?+0x0) [0x626f76dc0793]
(EE) 6: /usr/lib/x86_64-linux-gnu/libc.so.6 (__libc_start_call_main+0x81)
[0x75705722a601]
(EE) 7: /usr/lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main_alias_2+0x88)
[0x75705722a718]
(EE) 8: /usr/lib/xorg/Xorg (_start+0x25) [0x626f76da8005]
(EE) Segmentation fault at address 0x757057412ac8
Fatal server error:
(EE) Caught signal 11 (Segmentation fault). Server aborting
(EE) Server terminated with error (1). Closing log file.
Symbol matching
---------------
Installed Xorg executable build identifier:
8f5470187238a4a798f1bcfe384a0b46c432b4da.
Matching local debug symbols map WaitForSomething+0x195 to os/WaitFor.c:209,
immediately after the call to ospoll_wait. This identifies the
event-wait/dispatch path, but not the failing callback. The abbreviated libc
frame name is reproduced as logged and is not treated as proof that libc itself
is defective.
Relevant configuration and other software
-----------------------------------------
Xorg arguments, excluding machine-specific authentication paths:
-listen tcp -dumbSched :0 -seat seat0 -listen tcp vt7 -novtswitch
Kernel options, excluding disk identifiers:
ro pci=noaer acpi=ht irqpoll nomodset
-dumbSched was already configured as a workaround for a previously
investigated input-thread crash. This incident occurred despite that
setting. It is not established that this is the identical earlier
defect.
Synergy 3.8.4 was running as an X client. It crashed after the display
connection was already lost. Synergy had been updated from 3.7.2 before
the affected boot. There is insufficient evidence to identify Synergy as
the initiating cause.
libxtst6 was updated from 2:1.2.5-1build1 to 2:1.2.5-1ubuntu0.1 earlier
in the same boot. Xorg and libc were not updated during that interval.
These facts are supplied for triage, not as an assertion of causation.
Other checks and evidence limitations
------------------------------------
No out-of-memory kill, kernel panic, or i915 graphics-processor hang/reset was
found near the failure. The system-activity sample approximately 26 seconds
before USB removal showed approximately 25.8 GB available memory; the preceding
processor sampling interval was approximately 92.4% idle. This was not a full
operating-system crash: the subsequent requested reboot shut down normally.
Apport recorded that it skipped a fresh Xorg report because an earlier
unseen report already existed in its active report slot. That earlier
report concerns a different incident and is deliberately not attached as
if it were this crash. No new core dump is available for this incident.
The usual Xorg .old log had already been replaced by the replacement
greeter server's log. The fatal output above was preserved from
LightDM's X-server stderr log; that log also records startup of the
replacement server. A clean exit in the replacement server's log does
not describe the original crashing server.
Privacy
-------
This submission contains selected technical evidence only. Usernames,
hostnames, home-directory paths, company/project details, device serial
numbers, network addresses, disk identifiers, credentials, and unrelated
application logs have been omitted. No raw core dump, full system journal,
automatic diagnostic bundle, or original unredacted log is attached.
** Affects: xorg-server (Ubuntu)
Importance: Undecided
Status: New
--
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https://bugs.launchpad.net/bugs/2171491
Title:
Xorg SIGSEGV in event dispatch following Jabra Evolve2 65 USB hub
removal, terminating MATE session
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