Mullvad VPN crashes on Pixel 8, but does not on Pixel 7

Calculator Their support after not finding any crashes in app's logs (both internal and GrapheneOS') suggest me to disable hardened memory allocator, but I don't understand why, if it isn't needed on Pixel 7.

I think the (admittedly quite long) discussion in the following Github issue will shed some light on your question: https://github.com/mullvad/mullvadvpn-app/issues/6349

In short, Mullvad fixed a memory safety issue but there are apparently still issues that are uncovered by memory tagging usage with hardened_malloc on GrapheneOS. Seemingly more bugs are uncovered compared to running the app with memory tagging using Android's stock allocator (Scudo). When you disable hardened_malloc for an app while keeping memory tagging enabled for that app, the app will be running with the memory tagging implementation that is available on stock PixelOS (source).

Mullvad used to have a memory corruption bug upon each tunnel connect, which was revealed by MTE usage and Scudo (running the app with MTE enabled and hardened_malloc disabled used to crash the app on GrapheneOS), but Mullvad appears to have fixed that with a commit a few versions ago.

Calculator Can it be a hardware problem (I bought used Pixel 8 and cannot be 100% sure that it's hardware is untouched, Auditor's output seems OK)?

It is not a hardware problem. Memory tagging is working as intended.

Calculator Are there any differences in hardened malloc on different devices that can cause this?

There are some technical details on this in the Github issue I linked above – specifically in this comment by a GrapheneOS developer: https://github.com/mullvad/mullvadvpn-app/issues/6349#issuecomment-2381665133

de0u At some point, for security and privacy companies, the question should maybe become "Why aren't you testing your code on the most secure Android variant, which can uncover bugs that affect all Android platforms, including vulnerabilities?".

It's a very good point, and I think more companies should follow Mullvad's example by running their apps on GrapheneOS with memory tagging.

A user is reporting that there are no issues while running version 2024.9-beta. Is anyone able to confirm that running that version with Hardened malloc and memory tagging works fine?

Calculator Try changing servers. I haven't noticed any difference in connection quality compared to other versions.

Calculator also it allows me to change exit country, while Wireguard is limited in that: Mullvad VPN allows maximum 5 devices (Wireguard configurations, OpenVPN configurations and apps' logged in sessions combined)

No, actually. You can generate configs for multiple servers for the same private key (device), so you could have a config for dozens of different servers while only having one device registered.

It doesn't help your current case, because of the blocking problem in your country, but for someone else who might be unsure about using plain Wireguard, there is a solution for this.