Slack snap stopped working after ubuntu updates

[mwb]

I’m using the official slack snap from the snap store. I was no longer able to start slack, apparently because of recent apparmor changes in Ubuntu? it can no longer seem to be able to access /proc/<pid>/mem and refuses to start.

The workaround I found is to start it in x11 mode using slack --ozone-platform=x11 which is stupid, but works. The strange thing is, I did not need this, and it used to “Just Work” and now it broke, for me on Ubuntu 25.10 but ALSO for my coworker on 24.04 LTS. Is it a slack issue or an Ubuntu issue?

[Lin-Buo-Ren]

Topics regarding a specific snap belong to the snap topic category, I’ve fixed that for you.

[Lin-Buo-Ren]

You should contact the snap publisher for any issues encountered while using the snap:

[anilg04]

I also faced this same issue today. for resolution, I uninstalled slack from snap and installed the the previous version from snap store and it works for me (using Ubuntu 24.04.4 LTS)

[lizthegrey]

Digging into a crash on Ubuntu 24.04 / kernel 6.17 with slack snap rev 224 (4.47.69, promoted to stable channel last week around when this bug was reported) and rev 243 (4.49.84, beta), I’m fairly sure this is the same underlying bug — just with a different-looking symptom, the AppArmor thing may be a red herring.

Normally silent because bin/electron-launch redirects stderr to /dev/null. With sudo snap set slack debugmode=true:

ERROR:ui/gtk/gtk_ui.cc:257] Schema org.gnome.desktop.interface does not have key font-antialiasing
...
Segmentation fault (core dumped)

Under gdb, both revisions segfault at identical instruction patterns — a null-pointer virtual dispatch (mov (%rax),%rcx with rax=0; subsequent call *0x68(%rcx)) right after a GTK factory returns nullptr from the failed schema lookup. The previous rev 216 (4.46.99) isn’t affected.

Root cause: the snap declares default-provider: gnome-3-38-2004 (GNOME 3.38, ~2020), but font-antialiasing was added to org.gnome.desktop.interface in GNOME 42. The bundled Chromium queries it and the fallback path isn’t null-safe. Discord and Signal don’t hit this because they’re on newer gnome-* content slots.

Workaround that survives across restarts (but gets wiped on each snap refresh):

sudo snap set slack debugmode=true
snap run slack   # crashes; populates .last_revision
cp /usr/share/glib-2.0/schemas/gschemas.compiled \
   ~/snap/slack/current/.local/share/glib-2.0/schemas/
snap run slack   # now launches normally

Works because desktop-launch prepends $XDG_DATA_HOME to XDG_DATA_DIRS, so the injected file wins schema resolution over the stale gnome-3-38 copy. Single-XML injection does not work: the schema references enums in sibling schemas that glib-compile-schemas can’t resolve standalone — copying the host’s already-linked binary sidesteps that.

--ozone-platform=x11 likely “fixed” this for folks upthread by sidestepping the GTK settings bridge entirely rather than addressing the missing schema key.

Real fix is for Slack to bump the content plug to gnome-46-2404 in their snapcraft.yaml. Their snap recipe isn’t public so can’t PR it — emailing feedback@slack.com in parallel.

[ruario]

Thanks that does indeed work.

[mwb]

This is a very nice analysis; and I understand it’s Slacks “fault”, but what I can’t really understand is that we get this breakage half-way through an Ubuntu LTS release!

And the ‘promise’ of snap is that it causes isolation between your particular flavor of linux and your apps, and here the OS breaks the (indeed incorrectly declared) snap. This snap has got to be one of the more high profile ones and also snap installation is recommended by Slack itself!

[jocado]

@anilg04

for resolution, I uninstalled slack from snap and installed the the previous version from snap store and it works for me

You can just do snap revert {name_of_snap}to do that in a one liner.

Cheers,

Just

[jocado]

@mwb

This is a very nice analysis; and I understand it’s Slacks “fault”, but what I can’t really understand is that we get this breakage half-way through an Ubuntu LTS release!

This is a snap package from a third party, with no release engineering linked to LTS releases [ technically it uses a base staged from LTS release, but that doesn’t seem to be the problem here ]. It could be broken by them at any time, affecting multiple different distros and releases.

This doesn’t seem to be broken by the OS, it seems to be a snap change that wasn’t completed properly. The suggested fix above which looks reasonable to me, is

Slack to bump the content plug to gnome-46-2404

..which hasn’t really git much to do with the OS. You can presumably install that on any Ubuntu release.

Cheers,

Just

[jocado]

FYI - I also reported this to Slack last week. They said it was a known issue that they are looking into. I’m going to also share this thread with them via my support case.

Cheers,

Just

[mwb]

Ah! Then I misunderstood. I somehow thought this was an Ubuntu update breaking the Slack snap, but it was just the slack snap breaking in and of itself!

[lizthegrey]

correct, the snap was updated to a version that had incomplete/clashing dependencies. and somehow that was promoted to stable despite having that bug.

[jocado]

My device picked up rev 244 today. I’m tracking stable, so I assume they started a progressive release.

It still has the bug. Reverting again for now to take me back to 216

Cheers,

Just

[lizthegrey]

All: please try revision 246 on –beta channel (4.50.121). it appears to ship a working gschemas.compiled

[jocado]

I can confirm that’s working for me. Thanks!

In case anyone else is interested in doing the same, I’m keeping tracking stable, but have switched to that revision specifically.

snap refresh --revision 246 slack

Cheers,

Just

[jocado]

A couple of small issues though @lizthegrey

On launch, I always get asked this question:

This happens consistently every time, I’ve tried answering both Yes and No, the question is always asked again on next launch.

The theme doesn’t seem to quite match my current desktop theme. There’s a few things that appear differently, including the “mouse over” look, and the window min/max buttons. But that used to look the same as my desktop theme IIRC.

Are you able to comment on or take a look at both those issues, or should I raise another support ticket with Slack ?

Cheers,

Just

[lizthegrey]

I don’t work at Slack, would recommend filing /feedback for both issues yeah. I do repro both of those, the popup on launch, the mouse pointer looking weird when hovering over a channel in the list, but MOST IMPORTANTLY ``code blocks are broken``` and show in variable width font screams

[jocado]

@lizthegrey

I don’t work at Slac

Apologies - I don’t know why, but for some reason I assumed that

Strangely, code blocks seem ok for me.

Cheers,

Just

[jocado]

Oh. It;s also behaving oddly in window management, seems not quite alligned and misplaced at various times.

ok, so I’m going back to 216 after all.

Cheers,

Just