Re: [PATCH 4/4] Return -EINVAL if userspace passes bogus flags to open()

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

On Tue, Feb 12, 2019 at 09:54:47AM -0500, demiobenour@xxxxxxxxx wrote:
> From: "Demi M. Obenour" <demiobenour@xxxxxxxxx>
> 
> While testing the O_PATHSTATIC patch, I discovered that Linux does not
> return any error if an invalid flag is passed to open(2).  This prevents
> adding new flags without a (minor) risk of breaking userspace.
> Therefore, add a check for invalid flags, and return -EINVAL if any are
> found.

... which would qualtify as userland ABI breakage all by itself.