"Lock screen" does not actually lock anything

[aaime]

On a Linux Mint 18.1, I lock the screen either using "CTRL-ALT-L" or picking "lock screen" from the cinnamon menu. The lock screen with the clock appears, but at the first mouse movement or click it will unlock and return to the desktop immediately, without asking for a password.

[andromeda306]

Not sure whether this issue is still occurring for anyone else. But I'm still regularly experiencing problems with the lockscreen. Currently using cinnamon-screensaver 4.2.0, Cinnamon 4.2.4. Basically at what seem like random times I'll open up my laptop from suspended state (overnight) and the lockscreen won't even appear i.e the desktop is made available straight up. I'd say this is a pretty severe security issue and would appreciate any additional tips/questions. Happy to provide any additional system info if it can help solve the issue asap.

[codingthat]

Lately I've had this issue far less often, simply because I've left my external monitor unplugged, but it still does happen once in a while, I think when there's some complication like me closing the lid too quickly after hitting the keyboard shortcut to lock the screen. (Which is interesting, because I have it set to "do nothing" on lid closes.)

[andromeda306]

Most of the time I work with a usb-c dock for charging and external monitors attached and when I manually lock the screen (windows+L) I don't think there has been any issues. The issue most commonly occurs outside this setup, after I open up the laptop from system suspend at home or the next morning - in both cases prior to attaching external devices (apart from a usb keyboard which I am yet to rule out). It's worth noting that I've never experienced any scaling issues with the lockscreen, my problem is strictly limited to it being bypassed altogether. In addition I regularly experience the problem where the lockscreen seems unresponsive (when it works), no cursor flashing or keystrokes registered in the password field. However if I go ahead and authenticate the desktop appears as expected.

[McThump]

Some additional data points...

One computer here (a Dell OptiPlex 7010 with 2 monitors) is having this problem (timed auto-lock never occurs). The machine is running Cinnamon 3.8.8 on Debian 10.2, cinnamon-screensaver version 3.8.2.

(1) Restarting the computer resolves the problem for a few hours. (2) Disconnecting all peripherals except the monitors (in case something was injecting into a keyboard or mouse port) does not resolve the problem. (3) The problem does not occur when using xscreensaver instead of the cinnamon-screensaver.
(4) Most interesting is that after erasing the hard-drive and installing Windows 10, the problem also occurs with the native Windows screensaver. As with the Debian/Cinnamon setup, restarting Windows resolves the problem for a few hours.

Except for this screensaver issue, the computer works perfectly.

[andromeda306]

I'm currently running the most recent 19.3 version of Mint and I have to say, I think the problem is even worse than in previous releases. I'd be happy to provide further debug information to someone who is a bit more familiar with the inner workings of cinnamon. However as it stands, I'm going to reinvestigate implementing xscreensaver as I never got around to really fixing the issues lat time around.

[codingthat]

That would be fantastic! I find plugging/unplugging an HDMI cable (especially if the external screen takes over as your primary display whenever plugged in) exacerbates the issue even further. Hopefully a new implementation would take care of that too...

[qdinar]

aaime commented on 5 Jul 2017

... every time I unlock I can see the screen contents for a good while (1-2 seconds) before the lock screen appears and I can enter the password. ...

this happened once at my laptop, after waking it up, today. not long before i put it to sleep before this incident, a website, in firefox, used 100% cpu and something were using hdd much, as i heard. also, unusually many tabs were opened in firefox, as i remember.

Package: cinnamon-screensaver Version: 4.4.1+tricia

Package: cinnamon Version: 4.4.8+tricia

linux mint 19.3 64 bit.

[areographe]

Kernel: 5.4.31-1-MANJARO x86_64 bits: 64 Desktop: Cinnamon 4.4.8  Distro: Manjaro Linux 
cinnamon-screensaver 4.4.1

just had an issue where cinnamon-screensaver didn't run after rebooting, so pressing 'Lock' did nothing, and at the 15 minute mark (normal time before screensaver starts) the screen just turned off and moving the mouse woke it up again. no lock screen. using alt+f2 to run the command 'cinnamon-screensaver' seems to work now though.

[areographe]

just to follow up:

looks like this journalctl output is showing something related to the screensaver being killed before the bug appears

Apr 12 18:14:44 <host> cinnamon-session[1142]:_ WARNING: t+69865.21877s: Application 'cinnamon-settings-daemon-screensaver-proxy.desktop' killed by signal 15
Apr 12 14:34:57 <host> cinnamon-session[1142]: WARNING: t+56678.28012s: Application 'cinnamon-settings-daemon-screensaver-proxy.desktop' killed by signal 1
Apr 11 14:48:29 <host> cinnamon-session[1142]: WARNING: t+10958.45004s: Application 'cinnamon-settings-daemon-screensaver-proxy.desktop' killed by signal 1

i'm also getting these messages in journalctl as well:

Apr 12 17:15:42 luke-thinkpad cinnamon-session[1142]: WARNING: t+66323.01120s: Detected that screensaver has left the bus

prior to my last manjaro update i have 90% of my journalctl messages about the screensaver being detected appearing on the bus and only 10% being leaving the bus, but as of 2 days ago it's about 50-50.

hope this helps narrow it down