Bug#1075822: /usr/lib/x86_64-linux-gnu/libexec/kf5/kioslave5: kioslave5 loops infinitely when called with empty <klauncher-socket> argument

[Steffen Weinhart <stw392@blue-cable.de>]

Package: kio
Version: 5.115.0-6
Severity: normal
File: /usr/lib/x86_64-linux-gnu/libexec/kf5/kioslave5
X-Debbugs-Cc: stw392@blue-cable.de

Hi,

I stumbled upon some kind of two-fold bug. I'll begin with the second part
(which could as well be a bug on its own) because this is the most noticeable
part.
When kioslave5 is called with an empty string as third argument (<klauncher-
socket> as indicated in '--help' message), it loops infinitely resulting in
100% CPU utilization.
I can tell from inspecting with a debugger, that it keeps calling close()
repeatedly.
/proc/<pidof-kioslave>/cmdline shows two consecutive null bytes where the third
argument would be.
The problem can be seen for example when using ktorrent and connecting to any
http(s) tracker (like the torrents from cdimage.debian.org) or trying to open
an http(s) url pointing to a torrent file.
It can also be seen when using 'Save as' in Kate, but now with the thumbnail.so
module instead of kio_http.so, again with an empty string as 3rd arg.

This leads me to part one of this bug: Why is kioslave5 called with an empty
string? I cannot recall updating ktorrent or kate (or even kio) prior to this
bug showing up.
I'm not even sure if this is kio's fault or some other lib in between. But
wouldn't it be the responsibility of kioslave5 (or its modules) to at least
check for nonsense arguments and return with an error instead of looping
infinitely?


-- System Information:
Debian Release: trixie/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'stable-updates'), (500, 'stable-security'), (500, 'proposed-updates'), (500, 'unstable'), (500, 'stable'), (100, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 6.9.7 (SMP w/16 CPU threads; PREEMPT)
Kernel taint flags: TAINT_CPU_OUT_OF_SPEC
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=de
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages kio depends on:
ii  kded5                 5.115.0-2
ii  libacl1               2.3.2-2
ii  libc6                 2.38-13
ii  libgcc-s1             14-20240330-1
ii  libgssapi-krb5-2      1.21.2-1
ii  libkf5archive5        5.115.0-2
ii  libkf5authcore5       5.115.0-2
ii  libkf5configcore5     5.115.0-2
ii  libkf5configwidgets5  5.115.0-2
ii  libkf5coreaddons5     5.115.0-2
ii  libkf5dbusaddons5     5.115.0-2
ii  libkf5doctools5       5.115.0-2
ii  libkf5i18n5           5.115.1-2+b1
ii  libkf5itemviews5      5.115.0-2
ii  libkf5kiocore5        5.115.0-6
ii  libkf5kiogui5         5.115.0-6
ii  libkf5kiontlm5        5.115.0-6
ii  libkf5kiowidgets5     5.115.0-6
ii  libkf5notifications5  5.115.0-2
ii  libkf5service-bin     5.115.0-2
ii  libkf5service5        5.115.0-2
ii  libkf5solid5          5.115.0-2
ii  libkf5textwidgets5    5.115.0-2
ii  libkf5wallet-bin      5.115.0-2
ii  libkf5wallet5         5.115.0-2
ii  libkf5widgetsaddons5  5.115.0-2
ii  libkf5windowsystem5   5.115.0-2
ii  libqt5core5t64        5.15.13+dfsg-2
ii  libqt5dbus5t64        5.15.13+dfsg-2
ii  libqt5gui5t64         5.15.13+dfsg-2
ii  libqt5network5t64     5.15.13+dfsg-2
ii  libqt5qml5            5.15.13+dfsg-2
ii  libqt5widgets5t64     5.15.13+dfsg-2
ii  libqt5x11extras5      5.15.13-2
ii  libqt5xml5t64         5.15.13+dfsg-2
ii  libstdc++6            14-20240330-1
ii  libxml2               2.9.14+dfsg-1.3+b3
ii  libxslt1.1            1.1.35-1+b1

Versions of packages kio recommends:
pn  switcheroo-control  <none>
ii  systemsettings      4:5.27.11-1

kio suggests no packages.

-- no debconf information