Re: [RFC] shmgetfd idea

["H. Peter Anvin" <hpa@zytor.com>]

On 01/28/2014 03:14 PM, Kay Sievers wrote:
> 
> What would be the interface for additional functionality like
> sealing/unsealing that thing, that no operation can destruct its
> content as long as there is more than a single owner? That would be a
> new syscall or fcntl() with specific shmemfd options?
> 
> We also need to solve the problem that the inode does not show up in
> /proc/$PID/fd/, so that nothing can create a new file for it which we
> don't catch with the "single owner" logic. Or we could determine the
> "single owner" state from the inode itself?
> 

If the "single owner" is determined by the file structure (e.g. via a
fcntl as opposed to a ioctl), then presumably we would simply deny an
attempt to open the inode and create a new file structure for it.

On Linux, /proc/$PID/fd is an open as opposed to a dup (as much as I
personally don't like those semantics, they are well set in stone at
this point) so it satisfies your requirements.

	-hpa


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