[Boost-users] [Interprocess] Growing resets permissions

Subject: [Boost-users] [Interprocess] Growing resets permissions
From: Aaron_Wright_at_[hidden]
Date: 2012-09-10 12:28:05

        I have a situation where I don't know how much shared memory I 
need, so I made the shared memory grow when it ran out of space. My shared 
memory is shared between a process running as root and postgres, which 
won't run as root. So I set the permissions to unrestricted (0666) when I 
create the shared memory. My problem is that when I grow the shared 
memory, the permissions are reset to (0644). This breaks things, as 
postgres can no longer open the shared memory for writing.

        I followed the code a bit and saw that it was using ftruncate. 
Checking the man page for ftruncate reveals, "the set-user-ID and 
set-group-ID permission bits may be cleared."

        Has anyone else ran into this? What is the easy solution? Should I 
just set the permissions manually after growing? Is this a bug in the 
interprocess library?
---
Aaron Wright