Bug#969051: libgtk-3-0: Segfault with some radial gradients in theme

[Tobias Bengfort]

Package: libgtk-3-0
Version: 3.24.5-1
Severity: normal
Tags: upstream

Dear Maintainer,

I noticed that a specially crafted CSS theme causes all gtk3
applications to segfault. The issue seems to be related to some forms of
radial gradients, e.g.:

```
background: radial-gradient(ellipse farthest-side, blue, green);
```

I am not entirely sure if the syntax is even correct, but it should not result
in a segfault either way.


-- System Information:
Debian Release: 10.5
  APT prefers stable
  APT policy: (800, 'stable'), (600, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-10-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libgtk-3-0 depends on:
ii  adwaita-icon-theme   3.30.1-1
ii  hicolor-icon-theme   0.17-2
ii  libatk-bridge2.0-0   2.30.0-5
ii  libatk1.0-0          2.30.0-2
ii  libc6                2.28-10
ii  libcairo-gobject2    1.16.0-4
ii  libcairo2            1.16.0-4
ii  libcolord2           1.4.3-4
ii  libcups2             2.2.10-6+deb10u3
ii  libepoxy0            1.5.3-0.1
ii  libfontconfig1       2.13.1-2
ii  libfreetype6         2.9.1-3+deb10u1
ii  libgdk-pixbuf2.0-0   2.38.1+dfsg-1
ii  libglib2.0-0         2.58.3-2+deb10u2
ii  libgtk-3-common      3.24.5-1
ii  libharfbuzz0b        2.3.1-1
ii  libjson-glib-1.0-0   1.4.4-2
ii  libpango-1.0-0       1.42.4-8~deb10u1
ii  libpangocairo-1.0-0  1.42.4-8~deb10u1
ii  libpangoft2-1.0-0    1.42.4-8~deb10u1
ii  librest-0.7-0        0.8.1-1
ii  libsoup2.4-1         2.64.2-2
ii  libwayland-client0   1.16.0-1
ii  libwayland-cursor0   1.16.0-1
ii  libwayland-egl1      1.16.0-1
ii  libx11-6             2:1.6.7-1
ii  libxcomposite1       1:0.4.4-2
ii  libxcursor1          1:1.1.15-2
ii  libxdamage1          1:1.1.4-3+b3
ii  libxext6             2:1.3.3-1+b2
ii  libxfixes3           1:5.0.3-1
ii  libxi6               2:1.7.9-1
ii  libxinerama1         2:1.1.4-2
ii  libxkbcommon0        0.8.2-1
ii  libxml2              2.9.4+dfsg1-7+b3
ii  libxrandr2           2:1.5.1-1
ii  shared-mime-info     1.10-1

Versions of packages libgtk-3-0 recommends:
pn  libgtk-3-bin  <none>

Versions of packages libgtk-3-0 suggests:
ii  gvfs             1.38.1-5
ii  librsvg2-common  2.44.10-2.1

Versions of packages libgtk-3-0 is related to:
pn  appmenu-gtk3-module       <none>
pn  fcitx-frontend-gtk3       <none>
pn  gcin-gtk3-immodule        <none>
pn  gtk-vector-screenshot     <none>
pn  gtk3-engines-xfce         <none>
pn  gtk3-im-libthai           <none>
pn  hime-gtk3-immodule        <none>
pn  ibus-gtk3                 <none>
pn  imhangul-gtk3             <none>
ii  libcanberra-gtk3-module   0.30-7
pn  libcaribou-gtk3-module    <none>
pn  libgtk3-nocsd0            <none>
pn  maliit-inputcontext-gtk3  <none>
pn  packagekit-gtk3-module    <none>
pn  scim-gtk-immodule         <none>
pn  topmenu-gtk3              <none>
pn  uim-gtk3                  <none>
pn  uim-gtk3-immodule         <none>

-- no debconf information