System hangs with encrypted swap on kernel 6.5.0

[Chris Frey]

Using Ubuntu 22.04 LTS, and tested with both kernels linux-image-6.5.0-21-generic and gcp. Tested on VM's with 1G of RAM to make running out of swap easier. This behaviour does not happen on the 5.x kernel that I tested on the same VM.

If you create encrypted swap using the following steps, and then use lots of memory to trigger swap activity, it will eventually hang the entire system.

dd if=/dev/zero of=/swap.0 bs=1M count=1024
echo 'cryptswap.0 /swap.0 /dev/urandom swap,cipher=aes-cbc-essiv:sha256,size=256' >> /etc/crypttab
cryptdisks_start cryptswap.0
swapon /dev/mapper/cryptswap.0

A workaround was found, by creating a unencrypted swap file on an encrypted filesystem, which does not hang.