linux-kernel - Re: [RFC PATCH] NFS: Save 4 bytes when re-exporting

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sun, 12 Dec 2021 21:19:59 +0000
From:   Trond Myklebust <trondmy@...merspace.com>
To:     "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "richard@....at" <richard@....at>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>,
        "david@...ma-star.at" <david@...ma-star.at>
Subject: Re: [RFC PATCH] NFS: Save 4 bytes when re-exporting

On Sun, 2021-12-12 at 22:00 +0100, Richard Weinberger wrote:
> When re-exporting, the whole struct nfs_fh is embedded in the new
> fhandle.
> But we need only nfs_fh->data[], nfs_fh->size is not needed.
> So skip fs_fh->size and save a full word (4 bytes).
> The downside is the extra memcpy() in nfs_fh_to_dentry().
> 
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
> While investigating into improving NFS re-export I noticed that
> we can already save 4 bytes of overhead.
> I don't think we need to embedd the full struct nfs_fh and
> can skip ->size.
> 

NACK. This will break existing running clients. Any code to change the
filehandle format must be accompanied with code to detect and service
filehandles that are presented in the old format.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@...merspace.com