linux-kernel - Re: Have RESOLVE_* flags superseded AT

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Message-ID: <888183.1583160603@warthog.procyon.org.uk>
Date:   Mon, 02 Mar 2020 14:50:03 +0000
From:   David Howells <dhowells@...hat.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     dhowells@...hat.com, Florian Weimer <fweimer@...hat.com>,
        linux-api@...r.kernel.org, viro@...iv.linux.org.uk,
        metze@...ba.org, torvalds@...ux-foundation.org, cyphar@...har.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Have RESOLVE_* flags superseded AT_* flags for new syscalls?

Christian Brauner <christian.brauner@...ntu.com> wrote:

> I think we settled this and can agree on RESOLVE_NO_SYMLINKS being the
> right thing to do, i.e. not resolving symlinks will stay opt-in.
> Or is your worry even with the current semantics of openat2()? I don't
> see the issue since O_NOFOLLOW still works with openat2().

Say, for example, my home dir is on a network volume somewhere and /home has a
symlink pointing to it.  RESOLVE_NO_SYMLINKS cannot be used to access a file
inside my homedir if the pathwalk would go through /home/dhowells - this would
affect fsinfo() - so RESOLVE_NO_SYMLINKS is not a substitute for
AT_SYMLINK_NOFOLLOW (O_NOFOLLOW would not come into it).

David