linux-kernel - Re: [PATCH v4] pipe: use __pipe_{lock,unlock} instead of spinlock

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: <CAHk-=wjw-rrT59k6VdeLu4qUarQOzicsZPFGAO5J8TKM=oukUw@mail.gmail.com>
Date:   Sat, 28 Jan 2023 23:33:08 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Hongchen Zhang <zhanghongchen@...ngson.cn>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Christian Brauner (Microsoft)" <brauner@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        David Howells <dhowells@...hat.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        maobibo <maobibo@...ngson.cn>,
        Matthew Wilcox <willy@...radead.org>,
        Sedat Dilek <sedat.dilek@...il.com>
Subject: Re: [PATCH v4] pipe: use __pipe_{lock,unlock} instead of spinlock

On Sat, Jan 28, 2023 at 10:05 PM Hongchen Zhang
<zhanghongchen@...ngson.cn> wrote:
>
> Use spinlock in pipe_{read,write} cost too much time,IMO
> pipe->{head,tail} can be protected by __pipe_{lock,unlock}.
> On the other hand, we can use __pipe_{lock,unlock} to protect
> the pipe->{head,tail} in pipe_resize_ring and
> post_one_notification.

No, we really can't.

post_one_notification() is called under the RCU lock held, *and* with
a spinlock held.

It simply cannot do a sleeping lock like __pipe_lock().

So that patch is simply fundamentally buggy, I'm afraid.

                Linus