linux-kernel - Re: [PATCH 01/14] VFS: Add additional RESOLVE

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Date:   Tue, 10 Mar 2020 07:25:05 +0000
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com, Aleksa Sarai <cyphar@...har.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Stefan Metzmacher <metze@...ba.org>,
        Ian Kent <raven@...maw.net>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Christian Brauner <christian@...uner.io>,
        Jann Horn <jannh@...gle.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Karel Zak <kzak@...hat.com>, jlayton@...hat.com,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/14] VFS: Add additional RESOLVE_* flags [ver #18]

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> > > Also make openat2() handle RESOLVE_NO_TRAILING_SYMLINKS.
> 
> No, please let's not do this.
> 
> We have O_NOFOLLOW, and we can't get rid of it.
> 
> So adding RESOLVE_NO_TRAILING_SYMLINKS isn't a cleanup. It's just
> extra complexity for absolutely zero gain.

Okay.  So what's the equivalent of AT_SYMLINK_NOFOLLOW in RESOLVE_* flag
terms?  RESOLVE_NO_SYMLINKS is not equivalent, though O_NOFOLLOW is.  The
reason I ask is that RESOLVE_* flags can't be easily extended to non-open
syscalls that don't take O_* flags without it.  Would you prefer that new
non-open syscalls continue to take AT_* and ignore RESOLVE_* flags?  That
would be fine by me.

David