Public bug reported:
Summary
-------
Terminator crashes with SIGSEGV (NULL pointer dereference) inside
libpango-1.0.so.0 as soon as a character is printed that fontconfig
resolves to "Symbola". Removing the package fonts-symbola makes the
crash go away.
Environment
-----------
Kubuntu 24.04 (noble), X11
terminator 2.1.3-1
libvte-2.91-0 0.76.0-1ubuntu0.1
libpango-1.0-0 1.52.1+ds-1build1
fonts-symbola 2.60-1.1
Terminator profile: default font "Monospace" (-> Noto Sans Mono);
also reproduced with explicit "DejaVu Sans Mono Book 10".
Steps to reproduce
------------------
1. Install fonts-symbola on Kubuntu 24.04.
2. Start terminator.
3. Run: printf '\U0001F433\n'
(also crashes: printf '\u280b\u2819\u2839\n')
(does not crash: printf '\u2714\n')
Expected: the glyph is rendered (or a fallback is used).
Actual: terminator exits immediately.
Kernel log:
terminator[...]: segfault at 0 ip ... error 4 in
libpango-1.0.so.0.5200.1[256f4,...+39000]
(same offset 0x256f4 in every crash, at least 5 times)
Observations
------------
- `fc-match 'Symbola'` prints:
<unknown filename>: "Symbola" "Regular"
i.e. a match without a file.
- `fc-match -s 'Symbola'` lists that file-less entry first, then
NotoSansSymbols2-Regular.ttf (family "Symbola").
- `fc-list | grep -i symbola` shows "Symbola:style=Regular" without a
file, plus NotoSansSymbols2-Regular.ttf with family
"Symbola,Noto Sans Symbols2".
- /usr/share/fonts/truetype/ancient-scripts/Symbola_hint.ttf exists
(from fonts-symbola) but does not appear in `fc-list`.
- /etc/fonts/conf.avail/56-kubuntu-noto.conf contains a "Symbola" alias.
- xterm (no Pango) is not affected.
- After `sudo apt remove fonts-symbola && fc-cache -rfv` the crash no
longer occurs.
Hypothesis (not verified)
-------------------------
The fontconfig pattern without a file returned for "Symbola" is passed
to Pango, which dereferences a NULL font/file pointer. Possibly caused
by the combination of fonts-symbola and the Kubuntu alias. Pango should
skip such a pattern instead of crashing, regardless of the root cause.
Attached: apport crash report
(/var/crash/_usr_bin_terminator.1000.crash)
** Affects: pango1.0 (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "_usr_bin_terminator.1000.crash"
https://bugs.launchpad.net/bugs/2172153/+attachment/6012338/+files/_usr_bin_terminator.1000.crash
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https://bugs.launchpad.net/bugs/2172153
Title:
terminator segfaults in libpango-1.0.so.0 (NULL deref) when rendering
glyphs that fall back to "Symbola" with fonts-symbola installed on
Kubuntu 24.04
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