[SOLVED] Firefox 61.0.1 Hangs

[Dave Rove]

I'd been using Firefox 52esr with no problems, but since end-of-support is approaching, I've tried the latest Firefox 61.0.1 from the repository but it hangs. Thinking that it might be clashing with something else I'd installed, I placed a fresh install of Kubuntu 18.04.1 into a spare partition and tried again but got the same result. Konqueror and Chromium, however, work flawlessly.

Firefox's window appears with its usual header, but the page is blank.
I can type in a URL and hit return, but there's no response.
The settings menu ☰ opens but the options are mostly dysfunctional:
"Preferences" give no response.
"Customise" makes a new tab appear on the tab bar but that tab can't be selected.

Starting Firefox from the console gives a huge screed of errors (attached). The first lines are:
Unable to init server: Could not connect: Connection refused
(/usr/lib/firefox/firefox:1491): Gtk-WARNING **: 18:18:51.794: cannot open display: :0

Since nobody else seems to be having this problem, I assume it's something to do with my hardware, which runs Linux software flawlessly otherwise: Intel DQ77KB motherboard, i5-3470T CPU (with 2500 GPU).

I'd be grateful for suggestions on how to debug this.

(Edit: I should say Firefox is "dysfunctional" rather than "hung" since its window can be closed.)

[GreyGeek]

I also installed FireFox 61.0.1 from the repository. I also installed firefox-locale-en and xul-ext-ubufox
FF runs very nicely for me.

I made it the default browser in System Settings. I also removed all the default search engines except DuckDuckGo and I added Startpage and made it the default. I customized the tool bar by adding the email icon, so that when I click it while browsing it opens a write page for Thunderbird and makes the title of the web page the subject line and puts the link in the body of the email. All I do is occasionally add a comment and then fill in the to or bcc lines, and then send it.

[chimak111]

What happens when you run

firefox -safe-mode

from your terminal?

Are you using a profile carried over from the earlier version (52 ESR)?

If so, maybe some extension is to blame?

man firefox

has some other commands that may help you figure stuff out. I very much doubt it's a hardware issue.

[Dave Rove]

Thanks for the suggestions, chimak111.

Launching Firefox in safe mode didn't work either. Same problem.

My test installation was a fresh self-contained install to a separate partition with nothing carried over. I also deleted ~/.mozilla a few times.

I experimented with various command line options. I couldn't get the window to appear in debug mode. I found that I was able to open the "about:support" page if I supplied it as a URL on the command line. That gave a lot of info about the graphics subsytem (attached). With that page displayed, I found that I was then able to open a second tab, but it displayed the message "Gah. Your tab just crashed."

It doesn't seem to make much sense that this sort of thing would be related to my specific hardware, but I think I've eliminated any issues related to personal software-configuration. The only thing that I can point to is that the "HD Graphics 2500" GPU in the i5-3470T CPU is somewhat rare, and might be missed during software verification. It's a cut-down version of the "HD Graphics 4000" GPU, and I believe it's only used in dual-core Ivy Bridge CPUs. I've attached the output of graphics-relevant parts of "lspci" and "glxinfo".

I installed "ubuntu-desktop" in my test install and switched to Gnome on X, but that had the same problem. I switched to Gnome on Wayland -- and then Firefox sprang to life and worked flawlessly. This suggests that the problem is graphics-subsytem related, but doesn't tell me how to run Firefox on KDE.

Edit: I found that with the "about:config" displayed via command-line URL, I was then able to open "Preferences", which I couldn't before. I tried switching off hardware-acceleration but that didn't help.

[chimak111]

What about

**** user.js Preferences ****
Your profile folder contains a user.js file, which includes preferences that
were not created by Firefox.

in your graphics-info.txt? I don't have that.

BTW, when you access the about:support page, use "copy text to clipboard" and then paste the clipboard contents into a plain text editor. The formatting is nicer.

Overall, I don't know what to say given that you can run Firefox only in Wayland!

[Dave Rove]

Got it working!

After much speculative Googling for Ivy-Bridge-related Firefox bugs, I found a bug report (https://bugzilla.mozilla.org/show_bug.cgi?id=1419444) that said somebody's font-rendering problem was "a result of our new sandbox feature and a font on your system that is installed in a location that gets blocked by the sandbox". Although a dissimilar bug, it was something to try. I was able to open about:config by passing it as URL on the command line, and I started reducing the value of the key security.sandbox.content.level. I merely had to reduce it from 4 to 3 and all the problems went away.

It's a puzzle that it was set to 4 by default, because Mozilla's wiki page on the sandbox (https://wiki.mozilla.org/Security/Sandbox) only describes the effect of levels 1 to 3 — although there are 4 levels for Windows.

The bigger puzzle is why nobody else seems to be seeing this problem. I'll not mark this solved just yet because there's probably a bug that needs to be fixed somewhere, so I'll investigate a bit further.

(Edit: BTW, the "user.js preferences" thing seems to have been due to my switching off the hardware acceleration as described in the previous post — it went away after clearing ~/.mozilla again and had no affect on the issue.)

[chimak111]

I see "4" as well:

Sandbox
-------

Seccomp-BPF (System Call Filtering): true
Seccomp Thread Synchronization: true
User Namespaces: true
Content Process Sandboxing: true
Media Plugin Sandboxing: true
Content Process Sandbox Level: 4
Effective Content Process Sandbox Level: 4

Anyway, you got things going for you and that's great!

[GreyGeek]

Did your solution fix your "Gah. Your tab just crashed." problem?

[Dave Rove]

Yes, all symptoms are fixed with the settings hack.

I installed Ubuntu 18.04.1 (rather than Kubuntu) into a test partition, and surprisingly, Firefox worked just fine, both on Gnome X and on Gnome Wayland. I then installed the meta-package kubuntu-desktop, switched to the KDE desktop, and Firefox still worked fine. So on my PC, there's a difference between installing the Kubuntu distro, and installing the Ubuntu distro with KDE added. It doesn't work on the former (without a settings hack) but does work on the latter. This goes someway towards explaining why this fault hasn't been reported yet. Even if it's a fault that only manifests on dual-core Ivy Bridge CPUs, I'd have thought that it would be noticed if it failed on Ubuntu, which is ranked at no 3 on DistroWatch.com (Kubuntu is down at 39 with a fraction of the page hits).

I then tried the latest Neon. This time it didn't work without the settings hack.

I'm giving up and marking this as solved now, since it's fixed for me, although the root-cause bug is probably still going to be an issue for others. When I've got some time, I'll try the Mozillazine forums and then if appropriate a Mozilla mailing list to give the developers a prompt.

And, if anybody here finds that Firefox gets somewhat unreliable, remember this issue, and try reducing the sandbox security level.