linux-kernel - Re: [PATCH v5 5/7] revocable: Add fops replacement

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]

Message-ID: <aPo6CZyT_IGWmu-O@tzungbi-laptop>
Date: Thu, 23 Oct 2025 22:22:01 +0800
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Benson Leung <bleung@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	chrome-platform@...ts.linux.dev, linux-kselftest@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Simona Vetter <simona.vetter@...ll.ch>,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v5 5/7] revocable: Add fops replacement

On Tue, Oct 21, 2025 at 09:15:36AM -0300, Jason Gunthorpe wrote:
> On Tue, Oct 21, 2025 at 04:49:59AM +0000, Tzung-Bi Shih wrote:
> 
> > I didn't get the idea.  With a mutex, how to handle the opening files?
> > 
> > Are they something like: (?)
> > - Maintain a list for opening files in both .open() and .release().
> > - In misc_deregister_sync(), traverse the list, do something (what?), and
> >   wait for the userspace programs close the files.
> 
> You don't need any list, we don't want to close files.
> 
> Something like this, it is very simple. You can replace the rwsem with
> a srcu. srcu gives faster read locking but much slower sync.
> 
> [...]

I see.  The idea is basically the same but don't use revocable at all.

I was misunderstanding about the "sync" we were discussing for
misc_deregister_sync().  The "sync", is analogous to synchronize_srcu()
of revocable_provider_revoke() in the revocable version [1], doesn't wait
for closing all opened files.

[1] https://lore.kernel.org/chrome-platform/aPT-7TTgW_Xop99j@tzungbi-laptop/