-Rareru conjugates the same as ichidan verbs. So, semantically and syntactically it is possible to say:

Taberu -> Taberareru -> Taberarerareru

 

Korosu -> Korosareru -> Korosarerareru

However, it sounds unnatural like tongue twister. I'd rather use -Uru that indicates possibility (can; be possible):

'can be eaten' -> Taberareuru

 

'can be killed' -> Korosareuru

-Uru, N2 level grammar, is attached to the masu form verb stem.

Taberu -> Tabemasu -> Tabeuru

 

Korosu -> Koroshimasu -> Koroshiuru

-Rareru conjugates the same as ichidan verbs. So, semantically and syntactically it is possible to say:

Taberu -> Taberareru -> Taberarerareru

Korosu -> Korosareru -> Korosarerareru

However, it sounds unnatural like tongue twister. I'd rather use -Uru that indicates possibility (can; be possible):

'can be eaten' -> Taberareuru

'can be killed' -> Korosareuru

-Uru, N2 level grammar, is attached to the masu form verb stem.

Taberu -> Tabemasu -> Tabeuru

Korosu -> Koroshimasu -> Koroshiuru