doveadm: Error: open(/proc/self/io) failed

[Timo Sirainen]

On 31 Jul 2019, at 20.45, A. Schulze via dovecot <dovecot at dovecot.org> wrote:
> 
> 
> 
> Am 31.07.19 um 08:27 schrieb Sami Ketola via dovecot:
>> service lmtp {
>> user = vmail
>> }
>> 
>> please remove user = vmail from here or change it to root.
>> 
>> for security reasons lmtp service must be started as root since version 2.2.36. lmtp will drop root privileges after initialisation but it needs to open /self/proc/io as root before that.
> 
> Hello Sami,
> 
> I don't read "root is required for lmtp" in https://wiki.dovecot.org/LMTP#Security neither does https://dovecot.org/doc/NEWS-2.2 say so.
> Could you proof that statement somehow?


Alternative is:

service lmtp {
  user = vmail
  drop_priv_before_exec = yes
}

I'm not sure if you run into other problems with that.