[Bug] constant mangoapp coredump in Steam game mode: Permission denied: '/proc/<pid>/map_files'

[popsUlfr]

Describe the bug

When I add GamingModeLauncher.sh to Steam, in gaming mode it causes a constant stream of coredumps in mangoapp. This is not SteamOS on the Steam Deck but a Framework Desktop where I have a gamescope session for Steam that follows the one on SteamOS for the Steam Deck. I haven't tried on the Steam Deck yet.
Other than that, PartyDeck works as intended but the system gets flooded by coredumps.

To Reproduce
Steps to reproduce the behavior:

1. Add GamingModelauncher.sh to Steam
2. Switch to gaming mode or gamescope session Steam
3. Launch PartyDeck

Expected behavior
No coredumps with mangoapp.

Screenshots

Dec 17 00:14:50 fwd gamescope-session-plus[851159]: /usr/share/gamescope-session-plus/gamescope-session-plus: line 307: 1044420 Aborted                    (core dumped) mangoapp
Dec 17 00:14:50 fwd gamescope-session-plus[851159]: + true
Dec 17 00:14:50 fwd gamescope-session-plus[851159]: + mangoapp
Dec 17 00:14:51 fwd gamescope-session-plus[1044450]: [2025-12-17 00:14:51.038] [MANGOHUD] [error] [overlay_params.cpp:739] Unknown option 'nis_steam_sharpness'
Dec 17 00:14:51 fwd gamescope-session-plus[1044450]: terminate called after throwing an instance of 'ghc::filesystem::filesystem_error'
Dec 17 00:14:51 fwd gamescope-session-plus[1044450]:   what():  Permission denied: '/proc/1043939/map_files'
Dec 17 00:14:51 fwd systemd-coredump[1044478]: Process 1044450 (mangoapp) of user 1001 terminated abnormally with signal 6/ABRT, processing...
Dec 17 00:14:51 fwd systemd[1]: Started Process Core Dump (PID 1044478/UID 0).
Dec 17 00:14:51 fwd systemd-coredump[1044479]: [🡕] Process 1044450 (mangoapp) of user 1001 dumped core.
                                               
                                               Stack trace of thread 1044476:
                                               #0  0x00007fce4aaac56b pthread_kill (libc.so.6 + 0xac56b)
                                               #1  0x00007fce4aa44968 raise (libc.so.6 + 0x44968)
                                               #2  0x00007fce4aa2560f abort (libc.so.6 + 0x2560f)
                                               #3  0x0000564799f7398e n/a (/usr/bin/mangoapp + 0x3498e)
                                               #4  0x000056479a0eb69a n/a (/usr/bin/mangoapp + 0x1ac69a)
                                               #5  0x0000564799f738ae n/a (/usr/bin/mangoapp + 0x348ae)
                                               #6  0x000056479a0eb846 n/a (/usr/bin/mangoapp + 0x1ac846)
                                               #7  0x0000564799f58e05 n/a (/usr/bin/mangoapp + 0x19e05)
                                               #8  0x0000564799ffe2d8 n/a (/usr/bin/mangoapp + 0xbf2d8)
                                               #9  0x0000564799fa230c n/a (/usr/bin/mangoapp + 0x6330c)
                                               #10 0x0000564799f7f87f n/a (/usr/bin/mangoapp + 0x4087f)
                                               #11 0x000056479a176c44 n/a (/usr/bin/mangoapp + 0x237c44)
                                               #12 0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #13 0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044450:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa64df n/a (libc.so.6 + 0xa64df)
                                               #2  0x00007fce4ab33a0a __poll (libc.so.6 + 0x133a0a)
                                               #3  0x00007fce4ac5d3c3 n/a (libxcb.so.1 + 0xd3c3)
                                               #4  0x00007fce4ac5dc77 n/a (libxcb.so.1 + 0xdc77)
                                               #5  0x00007fce4ac5f085 xcb_wait_for_reply64 (libxcb.so.1 + 0xf085)
                                               #6  0x00007fce4af1c6a4 _XReply (libX11.so.6 + 0x4c6a4)
                                               #7  0x00007fce4aef9902 XInternAtom (libX11.so.6 + 0x29902)
                                               #8  0x0000564799f785b7 n/a (/usr/bin/mangoapp + 0x395b7)
                                               #9  0x00007fce4aa27b0b n/a (libc.so.6 + 0x27b0b)
                                               #10 0x00007fce4aa27bbb __libc_start_main (libc.so.6 + 0x27bbb)
                                               #11 0x0000564799f7def5 n/a (/usr/bin/mangoapp + 0x3eef5)
                                               
                                               Stack trace of thread 1044458:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044463:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044460:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044461:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044462:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044467:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aafb87e clock_nanosleep (libc.so.6 + 0xfb87e)
                                               #3  0x00007fce4ab0baf7 __nanosleep (libc.so.6 + 0x10baf7)
                                               #4  0x00007fce4ab40e9b usleep (libc.so.6 + 0x140e9b)
                                               #5  0x000056479a00ee95 n/a (/usr/bin/mangoapp + 0xcfe95)
                                               #6  0x000056479a176c44 n/a (/usr/bin/mangoapp + 0x237c44)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044459:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044464:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044468:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aafb87e clock_nanosleep (libc.so.6 + 0xfb87e)
                                               #3  0x00007fce4ab0baf7 __nanosleep (libc.so.6 + 0x10baf7)
                                               #4  0x000056479a0213f5 n/a (/usr/bin/mangoapp + 0xe23f5)
                                               #5  0x000056479a176c44 n/a (/usr/bin/mangoapp + 0x237c44)
                                               #6  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #7  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044477:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa64df n/a (libc.so.6 + 0xa64df)
                                               #2  0x00007fce4ab43138 __libc_msgrcv (libc.so.6 + 0x143138)
                                               #3  0x0000564799f7fcb8 n/a (/usr/bin/mangoapp + 0x40cb8)
                                               #4  0x000056479a176c44 n/a (/usr/bin/mangoapp + 0x237c44)
                                               #5  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #6  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044457:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044465:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               
                                               Stack trace of thread 1044466:
                                               #0  0x00007fce4aab2e62 n/a (libc.so.6 + 0xb2e62)
                                               #1  0x00007fce4aaa644f n/a (libc.so.6 + 0xa644f)
                                               #2  0x00007fce4aaa6bd7 n/a (libc.so.6 + 0xa6bd7)
                                               #3  0x00007fce4aaa987a pthread_cond_wait (libc.so.6 + 0xa987a)
                                               #4  0x00007fce476ae33e n/a (libgallium-25.3.1-arch1.3.so + 0x8ae33e)
                                               #5  0x00007fce4762102d n/a (libgallium-25.3.1-arch1.3.so + 0x82102d)
                                               #6  0x00007fce476ae26c n/a (libgallium-25.3.1-arch1.3.so + 0x8ae26c)
                                               #7  0x00007fce4aaaa4f8 n/a (libc.so.6 + 0xaa4f8)
                                               #8  0x00007fce4ab4131c n/a (libc.so.6 + 0x14131c)
                                               ELF object binary architecture: AMD x86-64
Dec 17 00:14:51 fwd systemd[1]: systemd-coredump@1396-36988-1044478_1044479-0.service: Deactivated successfully.
Dec 17 00:14:51 fwd systemd[1]: systemd-coredump@1396-36988-1044478_1044479-0.service: Consumed 114ms CPU time, 139.7M memory peak.

Logs

[partydeck] Monitors detected:
[partydeck] gamescope 28" (1920x1080)
[partydeck] Launching kwin session: "kwin_wayland" "--xwayland" "--width" "1920" "--height" "1080" "--exit-with-session" "\"./partydeck\" \"--fullscreen\""
[partydeck] Monitors detected:
[partydeck] X11-0 169093200" (1920x1080)
[partydeck] Starting eframe app...

Setup Information

• Linux Distro: CachyOS
• Hardware: Framework Desktop
• gamescope version 3.16.17

Additional context
So, mangoapp tries to read the mapped files at /proc/<pid>/map_files where pid corresponds to the kwin_wayland process spawned by partydeck. And they are indeed only root readable for some reason and I don't understand why.

[davidawesome02-backup]

Not sure why they are only readable by root, but I do have a question; are you wrapping mangohud around the game process or the entire partydeck launcher?

We should most likely add a setting (if @wunnr wants, I can do it too) to enable gamescope on each game via the gamescope argument so it is properly embedded and problems like this are not likely, but because you manually added it, we need more context as to what exactly you did to cause this.

Dec 17 00:14:50 fwd gamescope-session-plus[851159]: + true
Dec 17 00:14:50 fwd gamescope-session-plus[851159]: + mangoapp

seams to imply you may be running gamescope around partydeck who launches kwin, and then multiple instances of gamescope 👀

can you please send exactly what you are doing so we can try to help more :)

maybe wunnr has more insight, but this is just what I see at a glance.

[wunnr]

The extent of my knowledge here is that I know the gaming mode on official SteamOS uses their own variant of mangohud for the performance HUD. I don't know if gamescope-session-plus does something differently, but I am aware that other users have had issues when running partydeck with the performance HUD turned on

[popsUlfr]

I tested on the Steam Deck and same issue, although it fails already at reading /proc/<pid>/fdinfo:

Dec 17 10:06:46 sakuradeck mangoapp[27751]: [2025-12-17 10:06:46.969] [MANGOHUD] [error] [overlay_params.cpp:733] Unknown option 'nis_steam_sharpness'
Dec 17 10:06:47 sakuradeck mangoapp[27751]: [2025-12-17 10:06:47.020] [MANGOHUD] [error] [cpu.cpp:624] Could not find cpu temp sensor location
Dec 17 10:06:47 sakuradeck mangoapp[27751]: terminate called after throwing an instance of 'ghc::filesystem::filesystem_error'
Dec 17 10:06:47 sakuradeck mangoapp[27751]:   what():  Permission denied: '/proc/27418/fdinfo'

These files are root owned too on SteamOS.

@davidawesome02-backup mangohud is an integral part of the SteamOS gaming mode, it is integrated as mangoapp in gamescope. And gamescope wraps Steam as a whole in gaming mode.

If coredumps are not disabled at the system level, this will completely fill and thrash the SSD eventually.

But I'm not sure mango should really fail this spectacularly if it is unable to read these files.

[popsUlfr]

I found a workaround, simply by copying kwin_wayland to another location in PATH.

On the Steam Deck I had already set up a bin path at ~/.local/bin/ in my PATH env var.

cp /usr/bin/kwin_wayland ~/.local/bin/

On my Framework Desktop i just used /usr/local/bin/:

cp /usr/bin/kwin_wayland /usr/local/bin/

(creating a symbolic link does not prevent issue, the binary needs to be copied)

This is enough to prevent any coredumps with mangoapp since all files in /proc/<pid>/ are user readable.
There's a special rule somewhere that treats /usr/bin/kwin_wayland differently and changes ownership of process files.

EDIT:
It might be safer to only override PATH for party deck

cp /usr/bin/kwin_wayland bin/

And modify GamingModeLauncher.sh:

--- GamingModeLauncher.sh.backup        2025-12-17 11:37:17.311746339 +0100
+++ GamingModeLauncher.sh       2025-12-17 11:36:02.164871841 +0100
@@ -1,2 +1,3 @@
 #!/bin/bash
+export PATH="$(realpath bin):$PATH"
 ./partydeck --kwin --fullscreen > log.txt

[davidawesome02-backup]

@davidawesome02-backup mangohud is an integral part of the SteamOS gaming mode, it is integrated as mangoapp in gamescope. And gamescope wraps Steam as a whole in gaming mode.

Sorry, yes I know, I was mainly asking because if you had added it manually that could have been the problem in part too; I was not sure if you added the game with a wrapper script. I was asking wunnr if he wanted to use the --mango-app option on the embedded gamescope sessions so it would be under kwin anyway, and just advise people to not use wrappers like the one steam is doing here.

Good to hear you found a resolution to this at least temporarily, you may want to open a issue upstream though, because failing to load mangohud/app should not cause crashes or coredumps, and is not something under our domain with this project.