Being able to run a bunch of commands that would normally require root (such as killing every process, remounting all filesystems read-only etc.) as an unprivileged user doesn’t look very good. Sounds like a possible privilege escalation hole and/or a feature that can easily be abused.
That’s only the k
option of SysRq, not the whole thing.
How would the trojan be started at the login prompt anyway? That doesn’t really make sense.
We allow powering off with SysRq but disable everything else.
Also, it seems like Xen does support SysRq.
https://en.wikipedia.org/wiki/Magic_SysRq_key#Other_ways_to_invoke_Magic_SysRq
The Xen hypervisor has functionality to send magic commands to hosted domains via its xm sysrq command.[11] Additionally, a SysRq command can be invoked from a Xen paravirtual console by sending a break sequence Ctrl+O followed by the desired key.