Double free / Core dump if XDG_CONFIG_DIRS is set

[xaverdh]

Explicitly set the environment variable XDG_CONFIG_DIRS to something with more then 23 characters and try running

dunst --help

observe

free(): double free detected in tcache 2

(presumably from libc) followed by a core dump.

I think the double free occurs due to

dunst/src/settings.c

Line 77 in 660fdba

gchar * const xdg_config_dirs = xdg_cdirs && strnlen((gchar *) xdg_cdirs, 1)

as explained here: NixOS/nixpkgs#143043 (comment)

Installation info

• Version: 1.7.0
• Install type: package
• Distro and version: NixOS 21.11.20211026.113fcf3 (Porcupine)

[xaverdh]

Building with this commit xaverdh@32fc6da makes

env XDG_CONFIG_DIRS=aaaaaaaaaaaaaaaaaaaaaaaa dunst --help

succeed for me.
I am by no means an expert in C / low level programming, so there likely is a more elegant way to make the code correct..

[fwsmit]

Thanks for the report, it should be fixed with dc8efbb

[xaverdh]

I can confirm that the commit fixed the issue, thanks!