Re: [PATCH 2/4] Expose O_PATHSTATIC to userspace

[Andreas Dilger]

On Feb 12, 2019, at 7:54 AM, demiobenour@xxxxxxxxx wrote:
> 
> From: "Demi M. Obenour" <demiobenour@xxxxxxxxx>
> 
> This adds the file open flag O_PATHSTATIC, which ensures that symbolic
> links are *never* followed, even in path components other than the last.
> This is distinct from O_NOFOLLOW, which only prevents symlinks in the
> *last* component from being followed.
> 
> This is useful for avoiding race conditions in userspace code that
> should expose only a subset of the filesystem to clients.  This includes
> FTP and SFTP servers, QEMU, and others.
> 
> Currently, O_NOFOLLOW must be set if O_PATHSTATIC is set.  Otherwise,
> open() fails with -EINVAL.

I don't want to bikeshed (discard suggestion if you disagree), but why not
name the flag "O_NEVER_FOLLOW" so that users can see it is also related to
"O_NOFOLLOW"?  Otherwise it seems like they are two completely different
things from looking at the names, when in fact they are closely related.

Cheers, Andreas

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